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DotNet Interview Questions Answers

Question 1 : Differences between Datagrid, Datalist and Repeater?

Answer 1 : 1. Datagrid has paging while Datalist doesnt. 2. Datalist has a property called repeat. Direction = vertical/horizontal. (This is of great help in designing layouts). This is not there in Datagrid. 3. A repeater is used when more intimate control over html generation is required. 4. When only checkboxes/radiobuttons are repeatedly served then a checkboxlist or radiobuttonlist are used as they involve fewer overheads than a Datagrid. The Repeater repeats a chunk of HTML you write, it has the least functionality of the three. DataList is the next step up from a Repeater; accept you have very little control over the HTML that the control renders. DataList is the first of the three controls that allow you Repeat-Columns horizontally or vertically. Finally, the DataGrid is the motherload. However, instead of working on a row-by-row basis, you’re working on a column-by-column basis. DataGrid caters to sorting and has basic paging for your disposal. Again you have little contro, over the HTML. NOTE: DataList and DataGrid both render as HTML tables by default. Out of the 3 controls, I use the Repeater the most due to its flexibility w/ HTML. Creating a Pagination scheme isn't that hard, so I rarely if ever use a DataGrid. Occasionally I like using a DataList because it allows me to easily list out my records in rows of three for instance. I am constantly writing the drawing procedures with System.Drawing.Graphics, but having to use the try and dispose blocks is too time-consuming with Graphics objects. Can I automate this? Yes, the code System.Drawing.Graphics canvas = new System.Drawing.Graphics(); try { //some code } finally canvas.Dispose(); is functionally equivalent to using (System.Drawing.Graphics canvas = new System.Drawing.Graphics()) { //some code } //canvas.Dispose() gets called automatically

Question 2 : Difference between Class And Interface

Answer 2 : Class is logical representation of object. It is collection of data and related sub procedures with defination. Interface is also a class containg methods which is not having any definations. Class does not support multiple inheritance. But interface can support.

Question 3 : What doesu mean by .NET framework?

Answer 3 : The .NET Framework is an environment for building, deploying, and running Web Services and other applications. It consists of three main parts: the Common Language Runtime, the Framework classes, and ASP.NET

Question 4 : What’s the use of System.Diagnostics.Process class?

Answer 4 : By using System.Diagnostics.Process class, we can provide access to the files which are presented in the local and remote system.

Question 5 : What is the difference between "using System.Data;" and directly adding the reference from "Add References Dialog Box"?

Answer 5 : When u compile a program using command line, u add the references using /r switch. When you compile a program using Visual Studio, it adds those references to our assembly, which are added using "Add Reference" dialog box. While "using" statement facilitates us to use classes without using their fully qualified names. For example: if u have added a reference to "System.Data.SqlClient" using "Add Reference" dialog box then u can use SqlConnection class like this: System.Data.SqlClient.SqlConnection But if u add a "using System.Data.SqlClient" statement at the start of ur code then u can directly use SqlConnection class. On the other hand if u add a reference using "using System.Data.SqlClient" statement, but don't add it using "Add Reference" dialog box, Visual Studio will give error message while we compile the program.

Question 6 : What is Web.config?

Answer 6 : In classic ASP all Web site related information was stored in the metadata of IIS. This had the disadvantage that remote Web developers couldn't easily make Web-site configuration changes. For example, if you want to add a custom 404 error page, a setting needs to be made through the IIS admin tool, and you're Web host will likely charge you a flat fee to do this for you. With ASP.NET, however, these settings are moved into an XML-formatted text file (Web.config) that resides in the Web site's root directory. Through Web.config you can specify settings like custom 404 error pages, authentication and authorization settings for the Web sitempilation options for the ASP.NET Web pages, if tracing should be enabled, etc. The Web.config file is an XML-formatted file. At the root level is the tag. Inside this tag you can add a number of other tags, the most common and useful one being the system.web tag, where you will specify most of the Web site configuration parameters. However, to specify application-wide settings you use the tag. For example, if we wanted to add a database connection string parameter we could have a Web.config file like so.

Question 7 : ASP.NET Authentication Providers and IIS Security ?

Answer 7 : ASP.NET implements authentication using authentication providers, which are code modules that verify credentials and implement other security functionality such as cookie generation. ASP.NET supports the following three authentication providers: Forms Authentication: Using this provider causes unauthenticated requests to be redirected to a specified HTML form using client side redirection. The user can then supply logon credentials, and post the form back to the server. If the application authenticates the request (using application-specific logic), ASP.NET issues a cookie that contains the credentials or a key for reacquiring the client identity. Subsequent requests are issued with the cookie in the request headers, which means that subsequent authentications are unnecessary. Passport Authentication: This is a centralized authentication service provided by Microsoft that offers a single logon facility and membership services for participating sites. ASP.NET, in conjunction with the Microsoft® Passport software development kit (SDK), provides similar functionality as Forms Authentication to Passport users. Windows Authentication: This provider utilizes the authentication capabilities of IIS. After IIS completes its authentication, ASP.NET uses the authenticated identity's token to authorize access. To enable a specified authentication provider for an ASP.NET application, you must create an entry in the application's configuration file as follows: // web.config file

Question 8 : What is an Intermediate language?

Answer 8 : Assemblies are made up of IL code modules and the metadata that describes them. Although programs may be compiled via an IDE or the command line, in fact, they are simply translated into IL, not machine code. The actual machine code is not generated until the function that requires it is called. This is the just-in-time, or JIT, compilation feature of .NET. JIT compilation happens at runtime for a variety of reasons, one of the most ambitious being Microsoft's desire for cross-platform .NET adoption. If a CLR is built for another operating system (UNIX or Mac), the same assemblies will run in addition to the Microsoft platforms. The hope is that .NET assemblies are write-once-run-anywhere applications. This is a .NET feature that works behind-the-scenes, ensuring that developers are not limited to writing applications for one single line of products. No one has demonstrated whether or not this promise will ever truly materialize. CTS/CLS The MSIL Instruction Set Specification is included with the .NET SDK, along with the IL Assembly Language Programmers Reference. If a developer wants to write custom .NET programming languages, these are the necessary specifications and syntax. The CTS and CLS define the types and syntaxes that every .NET language needs to embrace. An application may not expose these features, but it must consider them when communicating through IL.

Question 9 : How can you automatically generate interface for the remotable object in .NET with Microsoft tools?

Answer 9 : the Soapsuds tool.

Question 10 : How to achieve Polymorphism in VB.Net?

Answer 10 : We can achieve polymarphism in .Net i.e Compile time polymarphism and Runtime polymarphism. Compiletime Polymarphism achieved by method overloading. Runtime polymarphism achieved by Early Binding or Late Binding. Provide the function pointer to the object at compile time called as Early Binding. provide the function pointer to the object at runtime called as Late Binding class emp having the method display() class dept having the method display() create objects as in the main function // Early binding dim obj as new emp dim ob as new dept obj.display()-to call the display method of emp class ob.display-to call the display method of the dept class // Late binding create object in the main class as object obj obj=new emp obj.display()-to call the display of emp class obj=new dept obj.display()-to call the display of dept class

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