A Design Pattern essentially consists of a problem in a software design and a solution to the same. In Design Patterns each pattern is described with its name, the motivation behind the pattern and its applicability.
According to MSDN, "A design pattern is a description of a set of interacting classes that provide a framework for a solution to a generalized problem in a specific context or environment. In other words, a pattern suggests a solution to a particular problem or issue in object-oriented software development.
Benefits of Design Patterns
The following are some of the major advantages of using Design Patterns in software development.
• Flexibility • Adaptability to change • Reusability
When to use Design Patterns
Design Patterns are particularly useful in one of the following scenarios.
• When the software application would change in due course of time.
• When the application contains source code that involves object creation and event notification.
When not to use Design Patterns
. Do not use design patterns in any of the following situations.
• When the software being designed would not change with time.
• When the requirements of the source code of the application are unique.
If any of the above applies in the current software design, there is no need to apply design patterns in the current design and increase unnecessary complexity in the design.
The Gang of Four (GOF) Patterns
The invention of the design patterns that we commonly use today can be attributed to the following four persons: Erich Gamma, Richard Helm, Ralph Johnson and John Vlissides. These men invented 23 patterns in all that are commonly known as the Gang of Four patterns or the GOF patterns.
• Creational • Structural • Behavioral
Each of these groups in turn contains related sub patterns.
Creational Patterns
The Creational Patterns deals with the best possible way of creating an object or an instance of a class. They simplify object creation and provide a flexible approach towards object creation. The following are the sub-patterns that fall under this group.
• Abstract Factory • Factory • Builder • Prototype • Singleton
Both the Abstract Factory and the Factory pattern have the same intent.
The Singleton Pattern indicates that there can be only one instance of a class throughout the Application’s life cycle. A singleton class is one that can be instantiated only once in the application domain and provides a global point of access to it.
Structural Patterns
Structural Patterns provides the flexibility to specify how objects and classes can interoperate. The following are the sub patterns that comprise the Structural Patterns group.
• Adapter • Façade • Bridge • Composite
• Decorator • Flyweight • Proxy • Adapter
• Bridge • Composite • Decorator • Flyweight
• Proxy
Behavioral Patterns
Behavioral patterns help you define a structure for inter-object communication between objects in your system. This design pattern is typically used to monitor the messages that are transmitted when the objects communicate in a system. The following are the sub patterns under Behavioral Patterns.
• Chain of Responsibility • Command • Interpreter • Iterator
• Mediator • Memento • Observer • State
• Strategy • Template Method • Visitor
ASP.NET MVC is a framework that allows developers to apply the MVC pattern in the development of an ASP.NET application, thus allowing a better separation of concerns, which results in better reusability and easier testing.
MVC consists of three kinds of objects
The Model is an application object.
The View is the screen presentation.
The controller defines the way the user interface reacts to user inputs
• The request comes from the client and hits the Controller.
• The Controller calls the Model in order to perform some "business" operations.
• The Model returns the results of the operations back to the Controller.
• The Controller decides which View needs to be rendered and sends it the data that must be rendered.
• Finally the View renders the output and sends the response back to the client.
What is Cryptography?
Cryptography is used to protect data and has many valuable uses. It can protect data from being viewed, modified, or to ensure the integrity from the originator. Cryptography can be used as a mechanism to provide secure communication over an unsecured network, such as the Internet, by encrypting data, sending it across the network in the encrypted state, and then the decrypting the data on the receiving end. Encryption can also be used as an additional security mechanism to further protect data such as passwords stored in a database to prevent them from being human readable or understandable.
Encryption Components
Encryption involves the use of a cryptography algorithm combined with a key to encrypt and decrypt the data. The goal of every encryption algorithm is to make it as difficult as possible to decrypt the data without the proper key. Data is translated from its originating form into something that appears meaningless unless the proper algorithm and key are used to decrypt the data.
The Microsoft .NET Framework classes (System.Security.Cryptography) will manage the details of cryptography for you. The classes are implemented with the same interface; so working with the classes is the same across the cryptography namespace.
Public-Key Encryption
Public-key encryption, also known as asymmetric encryption, uses a public and private key pair to encrypt and decrypt data. The public key is made available to anyone and is used to encrypt data to be sent to the owner of the private key. The private key, as the name implies, is kept private. The private key is used to decrypt the data and will only work if the correct public key was used when encrypting the data. The private key is the only key that will allow data encrypted with the public key to be decrypted. The keys can be stored for use multiple times, or generated for a one-time use.
Asymmetric encryption algorithms are usually efficient for encrypting small amounts of data only. The following public-key algorithms are available for use in the .NET Framework.
Digital Signature Algorithm (DSA)
RSA
Private-Key Encryption
Private-key Encryption, also known as symmetric encryption, uses a single key to encrypt and decrypt information. The key must be kept secret from those not authorized to decrypt the data lest the data be compromised. Private-key algorithms are relatively fast and can be used to encrypt and decrypt large streams of data. Private-key algorithms are known as block ciphers because they encrypt data one block at a time. A block cipher will encrypt the same input block into the same output block based on the algorithm and key. If the anything were known about the structure of the data, patterns could be detected and the key could possibly be reverse engineered. To combat this, the classes in the .NET Framework use a process known as chaining where information from the previous block is used in encrypting the current block. This helps prevent the key from being discovered. It requires an initialization vector (IV) be given to encrypt the first block of data.
The following private-key algorithms are available in the .NET Framework. Each description contains some basic information about each algorithm, including the strengths and weaknesses.
Data Encryption Standard (DES) algorithm encrypts and decrypts data in 64-bit blocks, using a 64-bit key. Even though the key is 64-bit, the effective key strength is only 56-bits. There are hardware devices advanced enough that they can search all possible DES keys in a reasonable amount of time. This makes the DES algorithm breakable, and the algorithm is considered somewhat obsolete.
RC2 is a variable key-size block cipher. The key size can vary from 8-bit up to 64-bits for the key. It was specifically designed as a more secure replacement to DES. The processing speed is two to three times faster than DES. However, the RC2CryptoServiceProvider available in the .NET Framework is limited to 8 characters, or a 64-bit key. The 8-character limitation makes it susceptible to the same brute force attack as DES.
TripleDES algorithm uses three successive iterations of the DES algorithm. The algorithm uses either two or three keys. Just as the DES algorithm, the key size is 64-bit per key with an effective key strength of 56-bit per key. The TripleDES algorithm was designed to fix the shortcomings of the DES algorithm, but the three iterations result in a processing speed three times slower than DES alone.
Rijndael algorithm, one of the Advanced Encryption Standard (AES) algorithms, was designed as a replacement for the DES algorithms. The key strength is stronger than DES, and was designed to out perform DES. The key can vary in length from 128, 192, to 256 bits in length. This is the algorithm I personally trust the most and that I'll use for the examples contained in the column.
Hashing Algorithms
No, I'm not talking about some type of drug related activity or an extra special recipe for brownies. Hashing refers to mapping data of any length into a fixed-length byte sequence. Regardless of if the input is the contents of the library of Congress or the typing test "The quick brown fox jumps over the lazy dog" it will result in an output of the same size. Hashing also produces unique results. Just as no two snowflakes are identical, no two combinations of input will produce the same hash output. Even if the input varies by a single character it will produce different output. The .NET Framework provides support for the following hash algorithms of which I'll leave it up to you to discover which one is right for you based on the size of the data you require.
HMACSHA1 MACTripleDES MD5CryptoServiceProvider SHA1Managed
SHA256Managed SHA384Managed SHA512Managed
How to Generate a Key and IV for Private-key Encryption
Each algorithm has specific key sizes that it expects for use. Each key must fit a predetermined size typically ranging from 1 character (8-bit) up to 32 characters (256-bit). Some of the algorithms support varying key sizes, but they must be within the valid ranges of key size for the particular algorithm. For our purposes, we'll use Rijndael, which supports 128, 192, and 256 bit keys. The way to generate a 128-bit key for use is through one of the hashing algorithms. A phrase, or "secret" of any length can be hashed to generate a key of the required size for encrypting data. The following code outlines a class containing a method that takes an input phrase and generates a key and IV for use.
Using Encryption to Protect Sensitive Data Stored in a Database
This brings us to a possible and often overlooked use for encryption, which is encrypting data such as passwords that are stored in a database. There are several benefits to storing sensitive data such as passwords in encrypted format.
It keeps sensitive application data such as passwords secret from those authorized to view data that ideally should not be able to see application specific data such as passwords.
It keeps passwords protected from unauthorized access. If the database is somehow compromised, the intruder must now the correct algorithm and key to decrypt the sensitive data.
Passing direct input to a query is dangerous because you never know what the input may contain. Suppose a stored procedure including something like "WHERE vc_Login = @Login and Password = @Password" is used for authentication. A user name of "'m' or 1=1" with the same for the password could evaluate to a true statement and result in incorrectly allowing access. If the user id and or password were stored encrypted then the data would not evaluate to a valid SQL statement because an encrypted form of the statement would be used in the evaluation.
22 New Features of Visual Studio 2008 for .NET Professionals
1. LINQ Support
LINQ essentially is the composition of many standard query operators that allow you to work with data in a more intuitive way regardless.
The benefits of using LINQ are significant – Compile time checking C# language queries, and the ability to debug step by step through queries.
2. Expression Blend Support
Expression blend is XAML generator tool for silverlight applications. You can install Expression blend as an embedded plug-in to Visual Studio 2008. By this you can get extensive web designer and JavaScript tool.
3. Windows Presentation Foundation
WPF provides you an extensive graphic functionality you never seen these before. Visual Studio 2008 contains plenty of WPF Windows Presentation Foundation Library templates. By this a visual developer who is new to .NET, C# and VB.NET can easily develop the 2D and 3D graphic applications.
Visual Studio 2008 provides free game development library kits for games developers. currently this game development kits are available for C++ and also 2D/3D Dark Matter one image and sounds sets.
4. VS 2008 Multi-Targeting Support
Earlier you were not able to working with .NET 1.1 applications directly in visual studio 2005. Now in Visual studio 2008 you are able to create, run, debug the .NET 2.0, .NET 3.0 and .NET 3.5 applications. You can also deploy .NET 2.0 applications in the machines which contains only .NET 2.0 not .NET 3.x.
5. AJAX support for ASP.NET
Previously developer has to install AJAX control library separately that does not come from VS, but now if you install Visual Studio 2008, you can built-in AJAX control library. This Ajax Library contains plenty of rich AJAX controls like Menu, TreeView, webparts and also these components support JSON and VS 2008 contains in built ASP.NET AJAX Control Extenders.
6. JavaScript Debugging Support
Since starting of web development all the developers got frustration with solving javascript errors. Debugging the error in javascript is very difficult. Now Visual Studio 2008 makes it is simpler with javascript debugging. You can set break points and run the javaScript step by step and you can watch the local variables when you were debugging the javascript and solution explorer provides javascript document navigation support.
7. Nested Master Page Support
Already Visual Studio 2005 supports nested master pages concept with .NET 2.0, but the problem with this Visual Studio 2005 that pages based on nested masters can't be edited using WYSIWYG web designer. But now in VS 2008 you can even edit the nested master pages.
8. LINQ Intellisense and Javascript Intellisense support for silverlight applications
Most happy part for .NET developers is Visual Studio 2008 contains intellisense support for javascript. Javascript Intellisense makes developers life easy when writing client side validation, AJAX applications and also when writing Silverlight applications
Intellisense Support: When we are writing the LINQ Query VS provides LINQ query syntax as tool tips.
9. Organize Imports or Usings
We have Organize Imports feature already in Eclipse. SInce many days I have been waiting for this feature even in VS. Now VS contains Organize Imports feature which removes unnecessary namespaces which you have imported. You can select all the namespaces and right click on it, then you can get context menu with Organize imports options like "Remove Unused Usings", "Sort Usings", "Remove and Sort". Refactoring support for new .NET 3.x features like Anonymous types, Extension Methods, Lambda Expressions.
10. Intellisense Filtering
Earlier in VS 2005 when we were typing with intellisense box all the items were being displayed. For example If we type the letter 'K' then intellisense takes you to the items starts with 'K' but also all other items will be presented in intellisense box. Now in VS 2008 if you press 'K' only the items starts with 'K' will be filtered and displayed.
11. Intellisense Box display position
Earlier in some cases when you were typing the an object name and pressing . (period) then intellisense was being displayed in the position of the object which you have typed. Here the code which we type will go back to the dropdown, in this case sometimes programmer may disturb to what he was typing. Now in VS 2008 If you hold the Ctrl key while the intellisense is dropping down then intellisense box will become semi-transparent mode.
12. Visual Studio 2008 Split View
VS 205 has a feature show both design and source code in single window. but both the windows tiles horizontally. In VS 2008 we can configure this split view feature to vertically, this allows developers to use maximum screen on laptops and wide-screen monitors.
Here one of the good feature is if you select any HTML or ASP markup text in source window automatically corresponding item will be selected in design window.
13. HTML JavaScript warnings, not as errors:
VS 2005 mixes HTML errors and C# and VB.NET errors and shows in one window. Now VS 2008 separates this and shows javascript and HTML errors as warnings. But this is configurable feature.
14. Debugging .NET Framework Library Source Code:
Now in VS 2008 you can debug the source code of .NET Framework Library methods. Lets say If you want to debug the DataBind() method of DataGrid control you can place a debugging point over there and continue with debug the source code of DataBind() method.
15. In built Silverlight Library
Earlier we used to install silverlight SDK separately, Now in VS 2008 it is inbuilt, with this you can create, debug and deploy the silverlight applications.
16. Visual Studio LINQ Designer
Already you know in VS 2005 we have inbuilt SQL Server IDE feature. by this you no need to use any other tools like SQL Server Query Analyzer and SQL Server Enterprise Manger. You have directly database explorer by this you can create connections to your database and you can view the tables and stored procedures in VS IDE itself. But now in VS 2008 it has View Designer window capability with LINQ-to-SQL.
17. Inbuilt C++ SDK
Earlier It was so difficult to download and configure the C++ SDK Libraries and tools for developing windows based applications. Now it is inbuilt with VS 2008 and configurable
18. Multilingual User Interface Architecture - MUI
MUI is an architecture contains packages from Microsoft Windows and Microsoft Office libraries. This supports the user to change the text language display as he wish.
Visual Studio is now in English, Spanish, French, German, Italian, Chinese Simplified, Chinese Traditional, Japanese, and Korean. Over the next couple of months. Microsoft is reengineering the MUI which supports nine local languages then you can even view Visual studio in other 9 local languages.
19. Microsoft Popfly Support
Microsoft Popfly explorer is an add-on to VS 2008, by this directly you can deploy or hosting the Silverlight applications and Marshup objects
Deployment Options Supported by .NET
You can deploy an ASP.NET Web application using any one of the following three deployment options.
XCOPY Deployment
Using the Copy Project option in VS .NET
Deployment using VS.NET installer
XCOPY Deployment
Before looking at how .NET enables XCOPY deployment, let us take a moment to understand what XCOPY deployment is. Prior to .NET, installing a component (for example, a COM Component) required copying the component to appropriate directories, making appropriate registry entries, and so on. But now in .NET, to install the component all you need to do is copy the assembly into the bin directory of the client application and the application can start using it right away because of the self-describing nature of the assembly. This is possible because compilers in the .NET Framework embed identifiers or meta-data into compiled modules and the CLR uses this information to load the appropriate version of the assemblies. The identifiers contain all the information required to load and run modules, and also to locate all the other modules referenced by the assembly. It is also refered to as zero-impact install since the machine is not impacted by way of configuring the registry entries and configuring the component. This zero-impact install also makes it possible to uninstall a component without impacting the system in any manner. All that is required to complete uninstallation is the removal of specific files from the specific directory. For performing this type of deployment, all you need to do is to go to the Command Prompt and copy over the required files to a specific directory on the server using the XCOPY command.
As you can see, the XCOPY command takes a number of arguments.
/ E - This option copies directories, subdirectories, and files of the source argument, including empty ones.
/ K - This option allows you to retain all the existing file and folder attributes. When you use XCOPY to copy files or a directory tree structure, XCOPY strips off file attributes by default. For example, if a file had the read-only attribute set, that attribute would be lost after the file is copied. To retain the original attributes with the copied files, you must use the / K parameter.
/ R - This option overwrites files marked as read only.
/ O - This option preserves all security-related permission ACLs of the file and folders.
/ H - This option copies both hidden and system files.
/ I - This option tells XCOPY to assume that the destination is a directory and create it if it does not already exist.
Once the folder is copied over to the target server, you then need to create a virtual directory on the target server (using Internet Information Manager MMC snap-in) and map that virtual directory to the physical directory that is created using the XCOPY command. That's all there is to deploying an ASP.NET Web application on a remote server using XCOPY Deployment.
Using the Copy Project Option in VS .NET
The Copy Project option in VS .NET makes it very easy to deploy ASP.NET Web applications onto the target servers. Using this option, you can copy the Web project to the same server or to a different server.
If you are using VS .NET to develop Web applicatons, the first thing that you need to do before packaging an ASP.NET Web applications is to change the Active Solution Configuration from Debug to Release as shown below. This allows the compiler not only to optimize the code but also remove the debugging related symbols from the code, making the code run much faster. To bring up the Configuration Manager, select your Web project from the Solution Explorer and select Project->Properties->Configuration Properties from the menu and then click on the Configuration Manager Command button. In the Active Solution Configuration combo box, select the Release option.
To copy the Web project onto the target server, select Project->Copy Project from the menu. Selecting that option will result in the following dialog box being displayed.
The Copy Project dialog provides the following options.
Destination Project Folder: Using this option, you can specify the location to which you want to copy the project. The location can be the same server or a remote server.
Web access method: The Web access method option determines the access method that is used to copy the Web project to the destination folder. There are two types of Web access methods.
File share: This option indicates that you want to directly access your project files on the Web server through a file share. It does not require FrontPage Server Extensions on the server.
FrontPage: This option specifies that you want to use the HTTP-based FrontPage Server Extensions to transfer your project files to the server. Before using this option, make sure FrontPage Server Extensions are installed on the server. This option will automatically create the required virtual directory on the target server.
Copy: The Copy option provides three types:
Only files needed to run this application: this option copies built output files (DLLs and references from the bin folder) and any content files (such as .aspx, .asmx files). Most of the time, you should be able to deploy the application using this default option.
All project files: this option copies built outputs (DLLs and references from the bin folder) and all files that are in the project. This includes the project file and source files.
All Files in the source project folder: choosing this option will result in all the project files and any other files that are in the project folder (or subfolder) being transferred to the destination folder.
To copy the Web project, select the appropriate options from the above Copy Project dialog box and click OK. This will result in the ASP.NET Web application being deployed on the target server.
Deployment Using VS .NET Web Setup Project
Even though XCOPY deployment and Copy Project options are very simple and easy-to-use, they do not lend themselves well to all of the deployment needs. For example, if your application requires more robust application setup and deployment requirements, VS .NET installer can be the right choice. Although you can distribute your Web application as a collection of build outputs, installer classes, and database creation scripts, it is often easier to deploy complex solutions with Windows Installer files. VS .NET provides Web setup projects that can be used to deploy Web applications. These Web setup projects differ from standard setup projects in that they install Web applications to a virtual root folder on a Web server rather than in the Program Files folder, as is the case with the applications installed using standard setup projects.
Since VS .NET installer is built on top of Windows Installer technology, it also takes advantages of Windows Installer features. Before starting on a discussion of VS .NET Web Setup Project, let us understand the architecture of Windows Installer technology that provides the core foundation on top of which the VS .NET installer is built.
Features Provided by VS .NET Web Setup Project
The deployment project in VS .NET builds on features of the Windows installer by allowing us to perform the following operations.
Reading or writing of registry keys
Creating directories in the Windows file system on the target servers
Provides a mechanism to register components
Provides a way to gather information from the users during installation
Allows you to set launch conditions, such as checking the user name, computer name, current operating system, software application installed, presence of .NET CLR and so on.
Also makes it possible to run a custom setup program or script after the installation is complete.
In the next section, we will see how to deploy our DeploymentExampleWebApp using the VS .NET Web Setup Project.
Creating a Web Setup Project Using VS .NET Installer
We will start by adding a new Web Setup Project to our DeploymentExampleWebApp ASP.NET Web application solution by selecting File->Add Project-> New Project from the menu. In the New Project dialog box, select Setup and Deployment Projects from the Project Types pane and then select Web Setup Project in the Templates pane as shown in the following figure.
After creating the project, you then need to add the output of the primary assembly and the content files of the ASP.NET Web application to the setup project. To do this, right click on the DeploymentExampleWebAppSetup project in the solution explorer and select Add->Project Output from the context menu. In the Add Project Output Group dialog box, select DeploymentExampleWebApp from the Project combo box and select Primary Output from the list.
After adding the project output, you then need to add the related Content Files (such as .aspx files, Images, and so on) to the project. To do this, again bring up the Add Project Output dialog box and then select Content Files from the list this time. It is illustrated in the following screenshot.
After adding the Primary output and the Content Files to the Web Setup project, the solution explorer looks as follows:
Configuring Properties through the Properties Window
There are a number of properties that you can set through the properties window of the Web Setup project. These properties determine the runtime display and behavior of the Windows installer file. To accomplish this, right click on the DeploymentExampleWebAppSetup project from the solution explorer and select Properties from the context menu to bring up its properties window. The dialog box shown below appears in the screen.
As can be seen from the above screenshot, the properties window provides properties such as Author, Description, Manufacturer, Support Phone and so on that can be very useful to the users (who are installing your application) of your application to get more details about your application.
Installing the ASP.NET Web Application
Once you have created the Windows installer file (.msi file), then installing the ASP.NET application in the target servers is very straightforward. All you need to do is to double-click on the .msi file from the Windows explorer. This will initiate the setup wizard, which will walk you through the installation steps. The following screenshot shows the first dialog box displayed during the installation.
Clicking on Next in the above dialog box results in the following dialog box, where you can specify the virtual directory that will be used to host this Web application. This is one of the handy features wherein the creation of virtual directory is completely automated obviating the need for manual intervention. In part two of this article, we will see how to set specific properties (such as Directory Security, Default Document and so on) on the virtual directory as part of the installation process.
In the above dialog box, you can also click on the Disk Cost... command button to get an idea of the space required for installing this Web application. Clicking on Next in the above dialog box results in the following dialog box where you are asked to confirm the installation.
When you click on Next in the above dialog box, the installation will begin and the application will be installed. If the application is successfully installed, you will see the following dialog box.
After installing the application, you can see the installed ASP.NET application through the Add/Remove Programs option (that can be accessed through Start->Settings->Control Panel) in your computer. From here, you can run the setup program to uninstall the application any time you want to.
Caching
The ability to store data in the main memory and then allow for retrieval of the same as and when they are requested.
Caching is a technique of persisting the data in memory for immediate access to requesting program calls.
ASP.NET supports three types of caching for Web-based applications:
1. Page Level Caching (called Output Caching)
2. Page Fragment Caching (often called Partial-Page Output Caching)
3. Programmatic or Data Caching
Output Caching
Output caching caches the output of a page (or portions of it) so that a page's content need not be generated every time it is loaded.
In a typical ASP.NET page, every time the user views the page, the Web server will have to dynamically generate the content of the page and perform the relevant database queries (which are a very expensive task to do).
Considering the fact that the page does not change for a certain period of time, it is always a good idea to cache whatever is non-static so that the page can be loaded quickly.
In Page Output Caching, the entire page is cached in memory so all the subsequent requests for the same page are addressed from the cache itself.
In Page Fragment Caching, a specific a portion of the page is cached and not the entire page. Page Output or Fragment Caching can be enabled or disabled at the Page, Application or even the Machine levels.
Data Caching allows us to cache frequently used data and then retrieve the same data from the cache as and when it is needed. We can also set dependencies so that the data in the cache gets refreshed whenever there is a change in the external data store. The external data store can be a file or even a database. Accordingly, there are two types to dependencies, namely, file based and Sql Server based. There are also differing cache expiration policies
Syntax: <%@ OutputCache Duration="60" VaryByParam="none" %>
The above syntax specifies that the page be cached for duration of 60 seconds and the value "none" for VaryByParam* attribute makes sure that there is a single cached page available for this duration specified.
* VaryByParam can take various "key" parameter names in query string. Also there are other attributes like VaryByHeader, VaryByCustom etc.
The following is the complete syntax of page output caching directive in ASP.NET.
<%@ OutputCache Duration="no of seconds" Location="Any Client Downstream Server None" VaryByControl="control" VaryByCustom="browser customstring" VaryByHeader="headers" VaryByParam="parameter" %>
To store the output cache for a specified duration
Declarative Approach:
<%@ OutputCache Duration="60" VaryByParam="None" %>
Programmatic Approach:
Response.Cache.SetExpires(DateTime.Now.AddSeconds(60));
Response.Cache.SetCacheability(HttpCacheability.Public);
• To store the output cache on the browser client where the request originated
Declarative Approach:
<%@ OutputCache Duration="60" Location="Client" VaryByParam="None" %>
Programmatic Approach:
Response.Cache.SetExpires(DateTime.Now.AddSeconds(60));
Response.Cache.SetCacheability(HttpCacheability.Private);
• To store the output cache on any HTTP 1.1 cache-capable devices including the proxy servers and the client that made request
Declarative Approach:
<%@ OutputCache Duration="60" Location="Downstream" VaryByParam="None" %>
Programmatic Approach:
Response.Cache.SetExpires(DateTime.Now.AddSeconds(60));
Response.Cache.SetCacheability(HttpCacheability.Public);
Response.Cache.SetNoServerCaching();
• To store the output cache on the Web server
Declarative Approach:
<%@ OutputCache Duration="60" Location="Server" VaryByParam="None" %>
Programmatic Approach:
TimeSpan freshness = new TimeSpan(0,0,0,60);
DateTime now = DateTime.Now;
Response.Cache.SetExpires(now.Add(freshness));
Response.Cache.SetMaxAge(freshness);
Response.Cache.SetCacheability(HttpCacheability.Server);
Response.Cache.SetValidUntilExpires(true);
• To cache the output for each HTTP request that arrives with a different City:
Declarative Approach:
<%@ OutputCache duration="60" varybyparam="City" %>
Programmatic Approach:
Response.Cache.SetExpires(DateTime.Now.AddSeconds(60));
Response.Cache.SetCacheability(HttpCacheability.Public);
Response.Cache.VaryByParams["City"] = true;
For the VaryByCustom attribute, the VaryByHeader attribute, and the VaryByParam attribute in the @ OutputCache directive, the HttpCachePolicy class provides the VaryByHeaders property and the VaryByParams
property, and the SetVaryByCustom method.
1. Page Output Caching
In Page Output Caching, the entire page is cached in memory so all the subsequent requests for the same page are addressed from the cache itself.
Partial-Page Output Caching/ Page Fragment Caching
In Page Fragment Caching, a specific a portion of the page is cached and not the entire page. Page Output or Fragment Caching can be enabled or disabled at the Page, Application or even the Machine levels.
More often than not, it is impractical to cache entire pages. For example, you may have some content on your page that is fairly static, such as a listing of current inventory, but you may have other information, such as the user's shopping cart, or the current stock price of the company, that you wish to not be cached at all. Since Output Caching caches the HTML of the entire ASP.NET Web page, clearly Output Caching cannot be used for these scenarios: enter Partial-Page Output Caching.
Partial-Page Output Caching, or page fragment caching, allows specific regions of pages to be cached.
fragment caching comes from the attribute "VaryByControl". Using this attribute one can cache a user control based on the properties exposed.
Syntax: <%@ OutputCache Duration="60" VaryByControl="DepartmentId" %>
The above syntax when declared within an *.ascx file ensures that the control is cached for 60 seconds and the number of representations of cached control is dependant on the property "DepartmentId" declared in the control.
Data Caching
Programmatic or data caching takes advantage of the .NET Runtime cache engine to store any data or object between responses. That is, you can store objects into a cache, similar to the storing of objects in Application scope in classic ASP.
Realize that this data cache is kept in memory and "lives" as long as the host application does. In other words, when the ASP.NET application using data caching is restarted, the cache is destroyed and recreated. Data Caching is almost as easy to use as Output Caching or Fragment caching: you simply interact with it as you would any simple dictionary object.
Note that the Insert method allows you to simply add items to the cache using a key and value notation as well. For example to simply add an instance of the object bar to the cache named foo, use syntax like this:
Cache.Insert("foo", bar); // C#
Cache.Insert("foo", bar) ' VB.NET
Question - Define Caching in ASP.NET.
Answer - Caching technique allows to store/cache page output or application data on the client. The cached information is used to serve subsequent requests that avoid the overhead of recreating the same information. This enhances performance when same information is requested many times by the user.
Question - Advantages of Caching
Answer - It increases performance of the application by serving user with cached output.
It decreases server round trips for fetching data from database by persisting data in the memory.
It greatly reduces overhead from server resources.
Question - What are the types of Caching in ASP.NET?
Answer - Caching in ASP.NET can be of the following types
Page Output Caching
Page Fragment Caching
Data Caching
Question - Explain in brief each kind of caching in ASP.NET.
Answer - Page Output Caching
This type of caching is implemented by placing OutputCache directive at the top of the .aspx page at design time.
For example:
<%@OutputCache Duration= "30" VaryByParam= "DepartmentId"%>
The duration parameter specifies for how long the page would be in cache and the VaryByParam parameter is used to cache different version of the page.
The VaryByParam parameter is useful when we require caching a page based on certain criteria.
Page Fragment Caching
This technique is used to store part of a Web form response in memory by caching a user control.
Data Caching
Data Caching is implemented by using Cache object to store and quick retrieval of application data.
Cache object is just like application object which can be access anywhere in the application.
The lifetime of the cache is equivalent to the lifetime of the application.
Question:-What do you mean by Share Point Portal ?
Answer: Here I have taken information regarding Share Point Portal Server 2003 provides mainly access to the crucial business information and applications. With the help of Share Point Server we can server information between Public Folders, Data Bases, File Servers and the websites that are based on Windows server 2003. This Share Point Portal is integrated with MSAccess and Windows servers, So we can get a Wide range of document management functionality. We can also create a full featured portal with readymade navigation and structure.
Question:-What is cross page posting in ASP.NET2.0 ?
Answer: When we have to post data from one page to another in application we used server.transfer method but in this the URL remains the same but in cross page posting there is little different there is normal post back is done but in target page we can access values of server control in the source page.This is quite simple we have to only set the PostBackUrl property of Button,LinkButton or imagebutton which specifies the target page. In target page we can access the PreviousPage property. and we have to use the @PreviousPageType directive. We can access control of PreviousPage by using the findcontrol method. When we set the PostBackURL property ASP.NET framework bind the HTML and Javascript function automatically.
Question: How to start Outlook,NotePad file in AsP.NET with code ?
Answer: Here is the syntax to open outlook or notepad file in ASP.NET VB.NET Process.Start("Notepad.exe") Process.Start("msimn.exe"); C#.NET System.Diagnostics.Process.Start("msimn.exe"); System.Diagnostics.Process.Start("Notepad.exe");
Question: What is the purpose of IIS ?
Answer: We can call IIS(Internet Information Services) a powerful Web server that helps us creating highly reliable, scalable and manageable infrastructure for Web application which runs on Windows Server 2003. IIS helps development center and increase Web site and application availability while lowering system administration costs. It also runs on Windows NT/2000 platforms and also for above versions. With IIS, Microsoft includes a set of programs for building and administering Web sites, a search engine, and support for writing Web-based applications that access database. IIS also called http server since it process the http request and gets http response.
Question: What is main difference between GridLayout and FormLayout ?
Answer: GridLayout helps in providing absolute positioning of every control placed on the page. It is easier to develop page with absolute positioning because control can be placed any where according to our requirement. But FormLayout is little different only experience Web Developer used this one reason is it is helpful for wider range browser. If there is absolute positioning we can notice that there are number of DIV tags. But in FormLayout whole work are done through the tables.
Question: How Visual SourceSafe helps Us ?
Answer: One of the powerful tool provided by Microsoft to keep up-to-date of files system its keeps records of file history once we add files to source safe it can be add to database and the changes ads by different user to this files are maintained in database from that we can get the older version of files to. This also helps in sharing,merging of files.
Question:-Can you define what is SharePoint and some overview about this ?
Answer: SharePoint helps workers for creating powerful personalized interfaces only by dragging and drop pre-defined Web Part Components. And these Web Parts components also helps non programmers to get information which care and customize the appearance of Web pages. To under stand it we take an example one Web Part might display a user's information another might create a graph showing current employee status and a third might show a list of Employees Salary. This is also possible that each functions has a link to a video or audio presentation. So now Developers are unable to create these Web Part components and make them available to SharePoint users.
Question:-What is different between WebUserControl and in WebCustomControl ?
Answer: Web user controls :- Web User Control is Easier to create and another thing is that its support is limited for users who use a visual design tool one good thing is that its contains static layout one more thing a separate copy is required for each application.
Web custom controls:-Web Custom Control is typical to create and good for dynamic layout and another thing is it have full tool support for user and a single copy of control is required because it is placed in Global Assembly cache.
Question:-What is Sandbox in SQL server and explain permission level in Sql Server ?
Answer: Sandbox is place where we run trused program or script which is created from the third party. There are three type of Sandbox where user code run.
Safe Access Sandbox:-Here we can only create stored procedure,triggers,functions,datatypes etc.But we doesnot have acess memory ,disk etc.
External Access Sandbox:-We cn access File systems outside the box. We can not play with threading,memory allocation etc.
Unsafe Access Sandbox:-Here we can write unreliable and unsafe code.
Question:-How many types of cookies are there in .NET ?
Answer: Two type of cookeies.
a) single valued eg request.cookies(”UserName”).value=”dotnetquestion”
b)Multivalued cookies. These are used in the way collections are used example
request.cookies(”CookiName”)(”UserName”)=”dotnetquestionMahesh”
request.cookies(”CookiName”)(”UserID”)=”interview″
Question: When we get Error 'HTTP 502 Proxy Error' ?
Answer: We get this error when we execute ASP.NET Web pages in Visual Web Developer Web server, because the URL randomly select port number and proxy servers did not recognize the URL and return this error. To resolve this problem we have to change settings in Internet Explorer to bypass the proxy server for local addresses, so that the request is not sent to the proxy.
Question:-What do you mean by three-tier architecture?
Answer: The three-tier architecture was comes into existence to improve management of code and contents and to improve the performance of the web based applications. There are mainly three layers in three-tier architecture. the are define as follows
(1)Presentation
(2)Business Logic
(3)Database
(1)First layer Presentation contains mainly the interface code, and this is shown to user. This code could contain any technology that can be used on the client side like HTML, JavaScript or VBScript etc.
(2)Second layer is Business Logic which contains all the code of the server-side .This layer have code to interact with database and to query, manipulate, pass data to user interface and handle any input from the UI as well.
(3)Third layer Data represents the data store like MS Access, SQL Server, an XML file, an Excel file or even a text file containing data also some additional database are also added to that layers.
Question: What is Finalizer in .NET define Dispose and Finalize?
Answer: We can say that Finalizer are the methods that's helps in cleanp the code that is executed before object is garbage collected .The process is called finalization . There are two methods of finalizer Dispose and Finalize .There is little diffrenet between two of this method .
When we call Dispose method is realse all the resources hold by an object as well as all the resorces hold by the parent object.When we call Dispose method it clean managed as well as unmanaged resources.
Finalize methd also cleans resources but finalize call dispose clears only the unmanged resources because in finalization the garbase collecter clears all the object hold by managed code so finalization fails to prevent thos one of methd is used that is: GC.SuppressFinalize.
Question: What is late binding ?
Answer: When code interacts with an object dynamically at runtime .because our code literally doesnot care what type of object it is interacting and with the methods thats are supported by object and with the methods thats are supported by object .The type of object is not known by the IDE or compiler ,no Intellisense nor compile-time syntax checking is possible but we get unprecedented flexibilty in exchange.if we enable strict type checking by using option strict on at the top of our code modules ,then IDE and compiler will enforce early binding behaviour .By default Late binding is done.
Question:-Does .NET CLR and SQL SERVER run in different process?
Answer: Dot Net CLR and all .net realtes application and Sql Server run in same process or we can say that that on the same address because there is no issue of speed because if these two process are run in different process then there may be a speed issue created one process goes fast and other slow may create the problem.
Question: The IHttpHandler and IHttpHandlerFactory interfaces ?
Answer: The IHttpHandler interface is implemented by all the handlers. The interface consists of one property called IsReusable. The IsReusable property gets a value indicating whether another request can use the IHttpHandler instance. The method ProcessRequest() allows you to process the current request. This is the core place where all your code goes. This method receives a parameter of type HttpContext using which you can access the intrinsic objects such as Request and Response. The IHttpHandlerFactory interface consists of two methods - GetHandler and ReleaseHandler. The GetHandler() method instantiates the required HTTP handler based on some condition and returns it back to ASP.NET. The ReleaseHandler() method allows the factory to reuse an existing handler.
Question: what is Viewstate?
Answer:View state is used by the ASP.NET page framework to automatically save the values of the page and of each control just prior to rendering to the page. When the page is posted, one of the first tasks performed by page processing is to restore view state.
State management is the process by which you maintain state and page information over multiple requests for the same or different pages.
Client-side options are:
* The ViewState property * Query strings * Hidden fields * Cookies
Server-side options are:
* Application state * Session state * DataBase
Use the View State property to save data in a hidden field on a page. Because ViewState stores data on the page, it is limited to items that can be serialized. If you want to store more complex items in View State, you must convert the items to and from a string.
ASP.NET provides the following ways to retain variables between requests:
Context.Handler object Use this object to retrieve public members of one Web form’s class from a subsequently displayed Web form.
Query strings Use these strings to pass information between requests and responses as part of the Web address. Query strings are visible to the user, so they should not contain secure information such as passwords.
Cookies Use cookies to store small amounts of information on a client. Clients might refuse cookies, so your code has to anticipate that possibility.
View state ASP.NET stores items added to a page’s ViewState property as hidden fields on the page.
Session state Use Session state variables to store items that you want keep local to the current session (single user).
Application state Use Application state variables to store items that you want be available to all users of the application.
Describe the security authentication flow and process in ASP.NET?
When a user requests a web page, there exists a process of security too, so that every anonymous user is checked for authentication before gaining access to the webpage. The following points are followed in the sequence for authentication when a client attempts a page request:
• A .aspx web page residing on an IIS web server is requested by an end user
• IIS checks for the user's credentials
• Authentication is done by IIS. If authenticated, a token is passed to the ASP.NET worker process along with the request
• Based on the authentication token from IIS, and on the web.config settings for the requested resource, ASP.NET impersonates the end user to the request thread. For impersonation, the web.config impersonate attribute's value is checked.
What is Authentication? What are the different types of Authentication?
In a client-server environment, there are plenty of cases where the server has to interact and identify the client that sends a request to the server. Authentication is the process of determining and confirming the identity of the client.
If a client is not successfully identified, it is said to be anonymous.
Windows Authentication Forms Authentication Passport Authentication
Essentially the Windows Authentication and Forms Authentication are the famous ones, as Passport Authentication is related to a few websites (like microsoft.com, hotmail.com, msn.com etc. only).
Windows Authentication is implemented mostly in Intranet scenarios. When a browser (client) sends a Request to a server where in windows authentication has been implemented, the initial request is anonymous in nature. The server sends back a Response with a message in HTTP Header. This Prompts a Window to display a Modal Dialog Box on the browser, where the end user may enter the "User name" and "Password".
The end user enters the credentials, which are then validated against the User Store on the Windows server. Note that each user who access the Web Application in a Windows Authentication environment needs to have a Windows Account in the company network.
How to avoid or disable the modal dialog box in a Windows Authentication environment?
By enabling the Windows Integrated Authentication checkbox for the web application through settings in IIS.
Forms Authentication is used in Internet based scenarios, where its not practical to provide a Windows based account to each and every user to the Web Server. In a Forms Authentication environment, the user enters credentials, usually a User Name and a corresponding Password, which is validated against a User Information Store, ideally a database table.
Forms Authentication Ticket is the cookie stored on the user's computer, when a user is authenticated. This helps in automatically logging in a user when he/she re-visits the website. When a Forms Authentication ticket is created, when a user re-visits a website, the Forms Authentication Ticket information is sent to the Web Server along with the HTTP Request.
Describe the Provider Model in ASP.NET 2.0?
The Provider model in ASP.NET 2.0 is based on the Provider Design Pattern that was created in the year 2002 and later implemented in the .NET Framework 2.0.
The Provider Model supports automatic creation of users and their respective roles by creating entries of them directly in the SQL Server (May even use MS Access and other custom data sources). So actually, this model also supports automatically creating the user table's schema.
The Provider model has 2 security providers in it: Membership provider and Role Provider. The membership provider saves inside it the user name (id) and corresponding passwords, whereas the Role provider stores the Roles of the users.
For SQL Server, the SqlMembershipProvider is used, while for MS Access, the AccessMembershipProvider is used. The Security settings may be set using the website adminstration tool. Automatically, the AccessMembershipProvider creates a Microsoft Access database file named aspnetdb.mdb inside the application's App_Data folder. This contains 10 tables.
Describe the Personalization in ASP.NET 2.0?
ASP.NET 2.0 Personalization - Personalization allows information about visitors to be persisted on a data store so that the information can be useful to the visitor when they visit the site again. In ASP.NET 2.0, this is controlled by a Personalization API. Before the Personalization Model came into existence, the prior versions of ASP.NET used of the old Session object to take care of re-visits. Now comes the Profile object.
In order to use a Profile object, some settings need to be done in web.config. The example below shall explain how to use a profile object:
//Add this to System.Web in web.config
'In Page_Load event, add the following...
If Profile.FirstName <> "" Then
Panel1.Visible = False
Response.Write("Welcome Back Dear :, " & Profile.FirstName & ", " & Profile.LastName)
Else
Panel1.Visible = True
End If
'Here is the code how to save the profile properties in an event to save it
Profile.FirstName = txtFirstName.Text
Explain about Generics?
Generics are not a completely new construct; similar concepts exist with other languages. For example, C++ templates can be compared to generics. However, there's a big difference between C++ templates and .NET generics. With C++ templates the source code of the template is required when a template is instantiated with a specific type. Contrary to C++ templates, generics are not only a construct of the C# language; generics are defined with the CLR. This makes it possible to instantiate generics with a specific type in Visual Basic even though the generic class was defined with C#.
Why we use Serialization?
Serialization of data using built-in .NET support makes persistence easy and reusable.
Most uses of serialization fall into two categories: persistence and data interchange. Persistence allows us to store the information on some non-volatile mechanism for future use. This includes multiple uses of our application, archiving, and so on. Data interchange is a bit more versatile in its uses. If our application takes the form of an N-tier solution, it will need to transfer information from client to server, likely using a network protocol such as TCP. To achieve this we would serialize the data structure into a series of bytes that we can transfer over the network. Another use of serialization for data interchange is the use of XML serialization to allow our application to share data with another application altogether. As you can see, serialization is a part of many different solutions within our application.
What is Serialization?
Serialization is the process of converting an object, or group of objects, into a form that can be persisted. When u serialize an object, you also serialize the values of its properties.
How Do You Use Serialization?
Serialization is handled primarily by classes and interfaces in the System.Runtime.Serialization namespace. To serialize an object, you need to create two things:
• A stream to contain the serialized objects.
• A formatter to serialize the objects into the stream.
The Role of Formatters in .NET Serialization
A formatter is used to determine the serialized format for objects. All formatters expose the IFormatter interface, and two formatters are provided as part of the .NET framework:
• BinaryFormatter provides binary encoding for compact serialization to storage, or for socket-based network streams. The BinaryFormatter class is generally not appropriate when data must be passed through a firewall.
• SoapFormatter provides formatting that can be used to enable objects to be serialized using the SOAP protocol. The SoapFormatter class is primarily used for serialization through firewalls or among diverse systems. The .NET framework also includes the abstract Formatter class that may be used as a base class for custom formatters. This class inherits from the IFormatter interface, and all IFormatter properties and methods are kept abstract, but you do get the benefit of a number of helper methods that are provided for you.
Advanced C# interview questions
.NET interview questions
1. What’s the advantage of using System.Text.StringBuilder over System.String? StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.
2. Can you store multiple data types in System.Array? No.
3. What’s the difference between the System.Array.CopyTo() and System.Array.Clone()? The first one performs a deep copy of the array, the second one is shallow.
4. How can you sort the elements of the array in descending order? By calling Sort() and then Reverse() methods.
5. What’s the .NET datatype that allows the retrieval of data by a unique key? HashTable.
6. What’s class SortedList underneath? A sorted HashTable.
7. Will finally block get executed if the exception had not occurred? Yes.
8. What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
9. Can multiple catch blocks be executed? No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.
10. Why is it a bad idea to throw your own exceptions? Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
11. What’s a delegate? A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
12. What’s a multicast delegate? It’s a delegate that points to and eventually fires off several methods.
13. How’s the DLL Hell problem solved in .NET? Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
14. What are the ways to deploy an assembly? An MSI installer, a CAB archive, and XCOPY command.
15. What’s a satellite assembly? When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
16. What namespaces are necessary to create a localized application? System.Globalization, System.Resources.
17. What’s the difference between // comments, /* */ comments and /// comments? Single-line, multi-line and XML documentation comments.
18. How do you generate documentation from the C# file commented properly with a command-line compiler? Compile it with a /doc switch.
19. What’s the difference between
XML documentation tag? Single line code example and multiple-line code example.
20. Is XML case-sensitive? Yes, so and are different elements.
21. What debugging tools come with the .NET SDK? CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.
22. What does the This window show in the debugger? It points to the object that’s pointed to by this reference. Object’s instance data is shown.
23. What does assert() do? In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
24. What’s the difference between the Debug class and Trace class? Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
25. Why are there five tracing levels in System.Diagnostics.TraceSwitcher? The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
26. Where is the output of TextWriterTraceListener redirected? To the Console or a text file depending on the parameter passed to the constructor.
27. How do you debug an ASP.NET Web application? Attach the aspnet_wp.exe process to the DbgClr debugger.
28. What are three test cases you should go through in unit testing? Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
29. Can you change the value of a variable while debugging a C# application? Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
30. Explain the three services model (three-tier application). Presentation (UI), business (logic and underlying code) and data (from storage or other sources).
31. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET? SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
32. What’s the role of the DataReader class in ADO.NET connections? It returns a read-only dataset from the data source when the command is executed.
33. What is the wildcard character in SQL? Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
34. Explain ACID rule of thumb for transactions. Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
35. What connections does Microsoft SQL Server support? Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).
36. Which one is trusted and which one is untrusted? Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
37. Why would you use untrusted verificaion? Web Services might use it, as well as non-Windows applications.
38. What does the parameter Initial Catalog define inside Connection String? The database name to connect to.
39. What’s the data provider name to connect to Access database? Microsoft.Access.
40. What does Dispose method do with the connection object? Deletes it from the memory.
41. What is a pre-requisite for connection pooling? Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.
Interview questions for C# developers
Useful for preparation, but too specific to be used in the interview.
1. Is it possible to inline assembly or IL in C# code? - No.
2. Is it possible to have different access modifiers on the get/set methods of a property? - No. The access modifier on a property applies to both its get and set accessors. What you need to do if you want them to be different is make the property read-only (by only providing a get accessor) and create a private/internal set method that is separate from the property.
3. Is it possible to have a static indexer in C#? - No. Static indexers are not allowed in C#.
4. If I return out of a try/finally in C#, does the code in the finally-clause run? - Yes. The code in the finally always runs. If you return out of the try block, or even if you do a “goto” out of the try, the finally block always runs:
using System;
class main
{
public static void Main()
{
try
{
Console.WriteLine("In Try block");
return;
}
finally
{
Console.WriteLine("In Finally block");
}
}
}
Both “In Try block” and “In Finally block” will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it’s a return without an expression (as it is above), the IL emitted is identical whether the return is inside or outside of the try. If the return has an expression, there’s an extra store/load of the value of the expression (since it has to be computed within the try block).
5. I was trying to use an “out int” parameter in one of my functions. How should I declare the variable that I am passing to it? - You should declare the variable as an int, but when you pass it in you must specify it as ‘out’, like the following: int i; foo(out i); where foo is declared as follows: [return-type] foo(out int o) { }
6. How does one compare strings in C#? - In the past, you had to call .ToString() on the strings when using the == or != operators to compare the strings’ values. That will still work, but the C# compiler now automatically compares the values instead of the references when the == or != operators are used on string types. If you actually do want to compare references, it can be done as follows: if ((object) str1 == (object) str2) { … } Here’s an example showing how string compares work:
7. using System;
8. public class StringTest
9. {
10. public static void Main(string[] args)
11. {
12. Object nullObj = null; Object realObj = new StringTest();
13. int i = 10;
14. Console.WriteLine("Null Object is [" + nullObj + "]n"
15. + "Real Object is [" + realObj + "]n"
16. + "i is [" + i + "]n");
17. // Show string equality operators
18. string str1 = "foo";
19. string str2 = "bar";
20. string str3 = "bar";
21. Console.WriteLine("{0} == {1} ? {2}", str1, str2, str1 == str2 );
22. Console.WriteLine("{0} == {1} ? {2}", str2, str3, str2 == str3 );
23. }
24. }
Output:
Null Object is []
Real Object is [StringTest]
i is [10]
foo == bar ? False
bar == bar ? True
25. How do you specify a custom attribute for the entire assembly (rather than for a class)? - Global attributes must appear after any top-level using clauses and before the first type or namespace declarations. An example of this is as follows:
26. using System;
27. [assembly : MyAttributeClass] class X {}
Note that in an IDE-created project, by convention, these attributes are placed in AssemblyInfo.cs.
28. How do you mark a method obsolete? -
[Obsolete] public int Foo() {...}
or
[Obsolete("This is a message describing why this method is obsolete")] public int Foo() {...}
Note: The O in Obsolete is always capitalized.
29. How do you implement thread synchronization (Object.Wait, Notify,and CriticalSection) in C#? - You want the lock statement, which is the same as Monitor Enter/Exit:
30. lock(obj) { // code }
translates to
try {
CriticalSection.Enter(obj);
// code
}
finally
{
CriticalSection.Exit(obj);
}
31. How do you directly call a native function exported from a DLL? - Here’s a quick example of the DllImport attribute in action:
32. using System.Runtime.InteropServices;
33. class C
34. {
35. [DllImport("user32.dll")]
36. public static extern int MessageBoxA(int h, string m, string c, int type);
37. public static int Main()
38. {
39. return MessageBoxA(0, "Hello World!", "Caption", 0);
40. }
41. }
This example shows the minimum requirements for declaring a C# method that is implemented in a native DLL. The method C.MessageBoxA() is declared with the static and external modifiers, and has the DllImport attribute, which tells the compiler that the implementation comes from the user32.dll, using the default name of MessageBoxA. For more information, look at the Platform Invoke tutorial in the documentation.
42. How do I simulate optional parameters to COM calls? - You must use the Missing class and pass Missing.Value (in System.Reflection) for any values that have optional parameters.
C# .NET interview questions
Good for preparation and general self-testing, but too specific for the actual job interview. This was sent in by a job applicant getting ready to step into the .NET field in India.
1. Are private class-level variables inherited? - Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.
2. Why does DllImport not work for me? - All methods marked with the DllImport attribute must be marked as public static extern.
3. Why does my Windows application pop up a console window every time I run it? - Make sure that the target type set in the project properties setting is set to Windows Application, and not Console Application. If you’re using the command line, compile with /target:winexe, not /target:exe.
4. Why do I get an error (CS1006) when trying to declare a method without specifying a return type? - If you leave off the return type on a method declaration, the compiler thinks you are trying to declare a constructor. So if you are trying to declare a method that returns nothing, use void. The following is an example: // This results in a CS1006 error public static staticMethod (mainStatic obj) // This will work as wanted public static void staticMethod (mainStatic obj)
5. Why do I get a syntax error when trying to declare a variable called checked? - The word checked is a keyword in C#.
6. Why do I get a security exception when I try to run my C# app? - Some security exceptions are thrown if you are working on a network share. There are some parts of the frameworks that will not run if being run off a share (roaming profile, mapped drives, etc.). To see if this is what’s happening, just move the executable over to your local drive and see if it runs without the exceptions. One of the common exceptions thrown under these conditions is System.Security.SecurityException. To get around this, you can change your security policy for the intranet zone, code group 1.2, (the zone that running off shared folders falls into) by using the caspol.exe tool.
7. Why do I get a CS5001: does not have an entry point defined error when compiling? - The most common problem is that you used a lowercase ‘m’ when defining the Main method. The correct way to implement the entry point is as follows: class test { static void Main(string[] args) {} }
8. What optimizations does the C# compiler perform when you use the /optimize+ compiler option? - The following is a response from a developer on the C# compiler team: We get rid of unused locals (i.e., locals that are never read, even if assigned). We get rid of unreachable code. We get rid of try-catch with an empty try. We get rid of try-finally with an empty try. We get rid of try-finally with an empty finally. We optimize branches over branches: gotoif A, lab1 goto lab2: lab1: turns into: gotoif !A, lab2 lab1: We optimize branches to ret, branches to next instruction, and branches to branches.
9. What is the syntax for calling an overloaded constructor within a constructor (this() and constructorname() does not compile)? - The syntax for calling another constructor is as follows: class B { B(int i) { } } class C : B { C() : base(5) // call base constructor B(5) { } C(int i) : this() // call C() { } public static void Main() {} }
10. What is the equivalent to regsvr32 and regsvr32 /u a file in .NET development? - Try using RegAsm.exe. Search MSDN on Assembly Registration Tool.
11. What is the difference between a struct and a class in C#? - From language spec: The list of similarities between classes and structs is as follows. Longstructs can implement interfaces and can have the same kinds of members as classes. Structs differ from classes in several important ways; however, structs are value types rather than reference types, and inheritance is not supported for structs. Struct values are stored on the stack or in-line. Careful programmers can sometimes enhance performance through judicious use of structs. For example, the use of a struct rather than a class for a Point can make a large difference in the number of memory allocations performed at runtime. The program below creates and initializes an array of 100 points. With Point implemented as a class, 101 separate objects are instantiated-one for the array and one each for the 100 elements.
12. My switch statement works differently than in C++! Why? - C# does not support an explicit fall through for case blocks. The following code is not legal and will not compile in C#:
13. switch(x)
14. {
15. case 0: // do something
16. case 1: // do something as continuation of case 0
17. default: // do something in common with
18. //0, 1 and everything else
19. break;
20. }
To achieve the same effect in C#, the code must be modified as shown below (notice how the control flows are explicit):
class Test
{
public static void Main() {
int x = 3;
switch(x)
{
case 0: // do something
goto case 1;
case 1: // do something in common with 0
goto default;
default: // do something in common with 0, 1, and anything else
break;
}
}
}
21. Is there regular expression (regex) support available to C# developers? - Yes. The .NET class libraries provide support for regular expressions. Look at the System.Text.RegularExpressions namespace.
22. Is there any sample C# code for simple threading? - Yes:
23. using System;
24. using System.Threading;
25. class ThreadTest
26. {
27. public void runme()
28. {
29. Console.WriteLine("Runme Called");
30. }
31. public static void Main(String[] args)
32. {
33. ThreadTest b = new ThreadTest();
34. Thread t = new Thread(new ThreadStart(b.runme));
35. t.Start();
36. }
}
37. Is there an equivalent of exit() for quitting a C# .NET application? - Yes, you can use System.Environment.Exit(int exitCode) to exit the application or Application.Exit() if it’s a Windows Forms app.
38. Is there a way to force garbage collection? - Yes. Set all references to null and then call System.GC.Collect(). If you need to have some objects destructed, and System.GC.Collect() doesn’t seem to be doing it for you, you can force finalizers to be run by setting all the references to the object to null and then calling System.GC.RunFinalizers().
39. Is there a way of specifying which block or loop to break out of when working with nested loops? - The easiest way is to use goto:
40. using System;
41. class BreakExample
42. {
43. public static void Main(String[] args) {
44. for(int i=0; i<3; j="0" j ="=" s =" #”n" s =" “’n" s =" @”n" s =" “n" a ="=" a =" new" unrestricted="true)]"> Which contains : Manifest - Meta data
versioning , Culture , IL, Reference
15. Describe the difference between inline and code behind - which is best in a loosely coupled solution Tightly coupled - INLINE
ANS: inline function bind at compile time can write in aspx page with in <% %>.
17. Explain what a diffgram is, and a good use for one
ANS : is an xml grammer. it talk about state of node in xml file.
18. Where would you use an iHTTPModule, and what are the limitations of any approach you might take in implementing one
ANS: Preprocessing before going to IIS.
20. What are the disadvantages of viewstate/what are the benefits
ANS : IT can be hacked . page is size is heavy.
21 Describe session handling in a webfarm, how does it work and what are the limits
ANS:
Session - mode
State sever
OUtprocess
sql
22. How would you get ASP.NET running in Apache web servers - why would you even do this?
ANS: ---- Install Mod_AspDotNet
Add at the end of C:\Program Files\Apache Group\Apache2\conf\httpd.conf the following lines
23. Whats MSIL, and why should my developers need an appreciation of it if at all?
ANS : Microsoft Intermeidate lanaguage. which is the out put for all the .net supported languages after comiplation will produce.
Appreciation for cross language support.
24. In what order do the events of an ASPX page execute. As a developer is it important to undertsand these events?
ANS : INIT, PageLoad, Prerender , UNload.
25. Which method do you invoke on the DataAdapter control to load your generated dataset with data?
Fill()
26. Can you edit data in the Repeater control?
NO
27. Which template must you provide, in order to display data in a Repeater control?
ITemtemplate
28. How can you provide an alternating color scheme in a Repeatercontrol?
AlternateItemTemplate
29. What property must you set, and what method must you call in your code, in order to bind the data from some data source to the Repeatercontrol?
Datasource,
DataBind
30. What base class do all Web Forms inherit from?
System.Web.UI.Page
31. What method do you use to explicitly kill a user s session?
abondon()
32 How do you turn off cookies for one page in your site?
disablecookies.
33. Which two properties are on every validation control?
control to validate, error message
34. What tags do you need to add within the asp:datagrid tags to bind
columns manually?
autogenerated columns is set to false
35. How do you create a permanent cookie?
Cooke = ne cookee().
cooke.adddate.
36. What tag do you use to add a hyperlink column to the DataGrid?
hyper link column
37. What is the standard you use to wrap up a call to a Web service
------------
38. Which method do you use to redirect the user to another page without performing a round trip to the client?
server.transfer
39. What is the transport protocol you use to call a Web service SOAP
http
40. True or False: A Web service can only be written in .NET
false
41. What does WSDL stand for? webservice discription language. it is used to generate for proxy( server object)
42. What property do you have to set to tell the grid which page to go to when using the Pager object?
Page Index.
43. Where on the Internet would you look for Web services?
UDDI
44. What tags do you need to add within the asp:datagrid tags to bind columns manually.
Autogenerate columns
45. Which property on a Combo Box do you set with a column name, prior to setting the DataSource, to display data in the combo box?
datatext
datavalue
46. How is a property designated as read-only?
get
47. Which control would you use if you needed to make sure the values in two different controls matched?
compare filed validator
48. True or False: To test a Web service you must create a windows application or Web application to consume this service?
no
49. How many classes can a single .NET DLL contain?
as many as u want..
1. Use of property in an interface:
An interface can have methods, properties, events and indexers. When a property in an interface is implemented in a class,
the advantage is that, through that property, the class can give access to its private member varibles.
1. What’s the implicit name of the parameter that gets passed into the class’ set method?
Value, and it’s datatype depends on whatever variable we’re changing.
2. How do you inherit from a class in C#?
Place a colon and then the name of the base class.
3. Does C# support multiple inheritance?
No, use interfaces instead.
4. When you inherit a protected class-level variable, who is it available to? Classes in the same namespace.
5. Are private class-level variables inherited?
Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.
6. Describe the accessibility modifier protected internal. It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).
7. C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?
Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.
8. What’s the top .NET class that everything is derived from? System.Object.
9. How’s method overriding different from overloading? When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
10. What does the keyword virtual mean in the method definition? The method can be over-ridden.
11. Can you declare the override method static while the original method is non-static?
No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.
12. Can you override private virtual methods? No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.
13. Can you prevent your class from being inherited and becoming a base class for some other classes?
Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It’s the same concept as final class in Java.
14. Can you allow class to be inherited, but prevent the method from being over-ridden?
Yes, just leave the class public and make the method sealed.
15. What’s an abstract class?
A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden. Essentially, it’s a blueprint for a class without any implementation.
16. When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)? When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
17. What’s an interface class?
It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.
18. Why can’t you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.
19. Can you inherit multiple interfaces? Yes, why not.
20. And if they have conflicting method names?
It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
21. What’s the difference between an interface and abstract class?
In the interface all methods must be abstract, in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.
22. How can you overload a method?
Different parameter data types, different number of parameters, different order of parameters.
23. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
24. What’s the difference between System.String and System.StringBuilder classes?
System.String is immutable, System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
25. Is it namespace class or class namespace? The .NET class library is organized into namespaces. Each namespace contains a functionally related group of classes so natural namespace comes first.
Can you can specify values for for variables in interfaces in c#?
(In Java you can)
Answer) NO. I tried this in VS.net and it gave me the following error:
D:\VisualStudio\…\Interface.cs(10): Interfaces cannot contain fields
1. What’s the implicit name of the parameter that gets passed into the class’ set method? Value, and its datatype depends on whatever variable we’re changing.
2. How do you inherit from a class in C#? Place a colon and then the name of the base class. Notice that it’s double colon in C++.
3. Does C# support multiple inheritance? No, use interfaces instead.
4. When you inherit a protected class-level variable, who is it available to? Classes in the same namespace.
5. Are private class-level variables inherited? Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.
6. Describe the accessibility modifier protected internal. It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).
7. C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write? Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.
8. What’s the top .NET class that everything is derived from? System.Object.
9. How’s method overriding different from overloading? When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
10. What does the keyword virtual mean in the method definition? The method can be over-ridden.
11. Can you declare the override method static while the original method is non-static? No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.
12. Can you override private virtual methods? No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.
13. Can you prevent your class from being inherited and becoming a base class for some other classes? Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It’s the same concept as final class in Java.
14. Can you allow class to be inherited, but prevent the method from being over-ridden? Yes, just leave the class public and make the method sealed.
15. What’s an abstract class? A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden. Essentially, it’s a blueprint for a class without any implementation.
16. When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)? When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
17. What’s an interface class? It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.
18. Why can’t you specify the accessibility modifier for methods inside the interface? They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.
19. Can you inherit multiple interfaces? Yes, why not.
20. And if they have conflicting method names? It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
21. What’s the difference between an interface and abstract class? In the interface all methods must be abstract; in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.
22. How can you overload a method? Different parameter data types, different number of parameters, different order of parameters.
23. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor? Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
24. What’s the difference between System.String and System.StringBuilder classes? System.String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
25. What’s the advantage of using System.Text.StringBuilder over System.String? StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.
26. Can you store multiple data types in System.Array? No.
27. What’s the difference between the System.Array.CopyTo() and System.Array.Clone()? The first one performs a deep copy of the array, the second one is shallow.
28. How can you sort the elements of the array in descending order? By calling Sort() and then Reverse() methods.
29. What’s the .NET datatype that allows the retrieval of data by a unique key? HashTable.
30. What’s class SortedList underneath? A sorted HashTable.
31. Will finally block get executed if the exception had not occurred? Yes.
32. What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
33. Can multiple catch blocks be executed? No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.
34. Why is it a bad idea to throw your own exceptions? Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
35. What’s a delegate? A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
36. What’s a multicast delegate? It’s a delegate that points to and eventually fires off several methods.
37. How’s the DLL Hell problem solved in .NET? Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
38. What are the ways to deploy an assembly? An MSI installer, a CAB archive, and XCOPY command.
39. What’s a satellite assembly? When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
40. What namespaces are necessary to create a localized application? System.Globalization, System.Resources.
41. What’s the difference between // comments, /* */ comments and /// comments? Single-line, multi-line and XML documentation comments.
42. How do you generate documentation from the C# file commented properly with a command-line compiler? Compile it with a /doc switch.
43. What’s the difference between and XML documentation tag? Single line code example and multiple-line code example.
44. Is XML case-sensitive? Yes, so and are different elements.
45. What debugging tools come with the .NET SDK? CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.
46. What does the This window show in the debugger? It points to the object that’s pointed to by this reference. Object’s instance data is shown.
47. What does assert() do? In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
48. What’s the difference between the Debug class and Trace class? Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
49. Why are there five tracing levels in System.Diagnostics.TraceSwitcher? The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
50. Where is the output of TextWriterTraceListener redirected? To the Console or a text file depending on the parameter passed to the constructor.
51. How do you debug an ASP.NET Web application? Attach the aspnet_wp.exe process to the DbgClr debugger.
52. What are three test cases you should go through in unit testing? Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
53. Can you change the value of a variable while debugging a C# application? Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
54. Explain the three services model (three-tier application). Presentation (UI), business (logic and underlying code) and data (from storage or other sources).
55. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET? SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
56. What’s the role of the DataReader class in ADO.NET connections? It returns a read-only dataset from the data source when the command is executed.
57. What is the wildcard character in SQL? Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
58. Explain ACID rule of thumb for transactions. Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
59. What connections does Microsoft SQL Server support? Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).
60. Which one is trusted and which one is untrusted? Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
61. Why would you use untrusted verificaion? Web Services might use it, as well as non-Windows applications.
62. What does the parameter Initial Catalog define inside Connection String? The database name to connect to.
63. What’s the data provider name to connect to Access database? Microsoft.Access.
64. What does Dispose method do with the connection object? Deletes it from the memory.
65. What is a pre-requisite for connection pooling? Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.
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