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Introduction to web service
A Web service is a class that allows its methods to be called by methods on other machines via common data formats and protocols, such as XML and HTTP. In .NET, the over-the-network method calls are commonly implemented through the Simple Object Access Protocol (SOAP), an XML-based protocol describing how to mark up requests and responses so that they can be transferred via protocols such as HTTP. Using SOAP, applications represent and transmit data in a standardized XML-based format.

A Web service is a software component stored on one machine that can be accessed by an application (or other software component) on another machine over a network. The machine on which the Web service resides is referred to as a remote machine. The application (i.e., the client) that accesses the Web service sends a method call over a network to the remote machine, which processes the call and returns a response over the network to the application.
Methods in a Web service are invoked through a Remote Procedure Call (RPC). These methods, which are marked with the WebMethod attribute, are often referred to as Web service methods or simply Web methods. Declaring a method with attribute WebMethod makes the method accessible to other classes through RPCs and is known as exposing a Web method.

Web services have important implications for business-to-business (B2B) transactions. They enable businesses to conduct transactions via standardized, widely available Web services rather than relying on proprietary applications. Web services and SOAP are platform and language independent, so companies can collaborate via Web services without worrying about the compatibility of their hardware, software and communications technologies.

Web services are not the best solution for certain performance-intensive applications, because applications that invoke Web services experience network delays. Also, data transfers are typically larger because data is transmitted in text-based XML formats.

Methods of a class that implement a Web service do not automatically have the ability to receive Web service requests and send back responses, but with Web services created using ASP.NET, it is very simple to add that capability. Apply a WebMethod attribute to public methods. Methods of a Web service class that can be communicated with over the Web are called Web service methods.

Web service methods are a key part of the messaging infrastructure employed by Web services. That is, a client and a Web service communicate using messages, specifically SOAP messages, by default. Clients send a SOAP request to a Web service and a Web service method typically returns a SOAP response. Web services define the type of messages they accept using operations, as defined by Web Services Description Language (WSDL). These operations correlate to each of the Web service methods within a Web service.

1. Explain the .NET architecture.
2. How many languages .NET is supporting now? - When .NET was introduced it came with several languages. VB.NET, C#, COBOL and Perl, etc. The site DotNetLanguages.Net says 44 languages are supported.
3. How is .NET able to support multiple languages? - a language should comply with the Common Language Runtime standard to become a .NET language. In .NET, code is compiled to Microsoft Intermediate Language (MSIL for short). This is called as Managed Code. This Managed code is run in .NET environment. So after compilation to this IL the language is not a barrier. A code can call or use a function written in another language.
4. How ASP .NET different from ASP? - Scripting is separated from the HTML, Code is compiled as a DLL, these DLLs can be executed on the server.
5. Resource Files: How to use the resource files, how to know which language to use?
6. What is smart navigation? - The cursor position is maintained when the page gets refreshed due to the server side validation and the page gets refreshed.
7. What is view state? - The web is stateless. But in ASP.NET, the state of a page is maintained in the in the page itself automatically. How? The values are encrypted and saved in hidden controls. this is done automatically by the ASP.NET. This can be switched off / on for a single control
8. Explain the life cycle of an ASP .NET page.
9. How do you validate the controls in an ASP .NET page? - Using special validation controls that are meant for this. We have Range Validator, Email Validator.
10. Can the validation be done in the server side? Or this can be done only in the Client side? - Client side is done by default. Server side validation is also possible. We can switch off the client side and server side can be done.
11. How to manage pagination in a page? - Using pagination option in DataGrid control. We have to set the number of records for a page, then it takes care of pagination by itself.
12. What is ADO .NET and what is difference between ADO and ADO.NET? - ADO.NET is stateless mechanism. I can treat the ADO.Net as a separate in-memory database where in I can use relationships between the tables and select insert and updates to the database. I can update the actual database as a batch.