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Interview Questions and Answers on .Net Framework, OOPS, ASP.Net, C#.Net, SQL Server, WCF Series – Part 37


Question 361 – What is a WSDL?

  • WSDL is an XML-based language for describing Web services and how to access them.
  • WSDL stands for Web Services Description Language
  • WSDL is written in XML
  • WSDL is an XML document
  • WSDL is used to describe Web services
  • WSDL is also used to locate Web services
  • WSDL is a W3C recommendation
  • A .wsdl file is an XML document written in an XML grammar.
  • It defines how an XML Web service behaves and instructs clients as to how to interact with service.

Question 362 – What are the elements of WSDL?

Below are the elements that are mainly used in WSDL.

<types>    The data types used by the web service
<message>    The messages used by the web service
<portType>    The operations performed by the web service
<binding>    The communication protocols used by the web service

Question 363 – What is a DISCO?

  • DISCO is Discovery of Web Services
  • It’s a document, which typically resides at the root of the web server.
  • Contains references to the location of available web services. 
  • It allows the discovery of services at a known URL.
  • It can define a document format along with an interrogation algorithm, making it possible to discover the Web Services exposed on a given server.
  • It is the discovery file which gives path to the Webservices
  • It contains WSDL When one searches for Web Services, it will go to the DISCO which gives actual info
    Disco.exe - The Web Services Discovery tool discovers URLs of XML Web services located on a Web server and saves documents related to each XML web service on local disk. Syntax - disco [options] URL

Question 364 – What is a VSDISCO?

  • VSDISCO files are DISCO files that support dynamic discovery of Web services.
  • ASP.NET links the VSDISCO to a HTTP handler that scans the host directory and subdirectories for ASMX and DISCO files and returns a dynamically generated DISCO document.
  • A client who requests a VSDISCO file gets back what appears to be a static DISCO document.
  • Microsoft is actively discouraging the use of VSDISCO files because they could represent a threat to Web server security.
  • VSDISCO files are disabled in the release version of ASP.NET. We can reenable them by uncommenting the line in the <httpHandlers> section of Machine.config

Question 365 – What are the different Protocols in webservice?

  • 3 Different protocols can be used such as Http-Get, Http-Post, and SOAP.
  • These protocols are included in the WSDL file that is automatically generated in .NET application.
  • It is preferable to use Http-Get and Http-Post only when name/value pairs of data is available

Question 366 – What are the component we get while Deploying Webservice?

  • Web application directory
  • web.config file
  • .asmx files
  • .disco files
  • Bin folder( containing dlls)
  • Keep alive ( for load balancing)

Question 367 – What is a Webservice protocol stack?

  • It is a set of protocols used to define, discover, and implement WS.
  • The protocol stack consists of 4 layers as follows
  • Service Transport: This layer is responsible for transferring messages between different applications. It includes HTTP, SMTP, FTP, and newer protocols such as Blocks Extensible Exchange Protocol (BEEP).
  • XML Messaging: This layer is responsible for encoding messages in a common XML format so that messages can be understand at either end. It includes XML-RPC and SOAP.
  • Service Description: This layer is responsible for describing the public interface to a specific Web service. This service description is handled via the WSDL.
  • Service Discovery: This layer is responsible for centralizing services into a common registry, and providing easy functionality. This service discovery is handled via the UDDI.

Question 368 – What is a XML-RPC?

  • It is a protocol that uses XML messages to perform Remote Procedure Calls.
  • Requests are encoded in XML and sent via HTTP POST;
  • XML responses are embedded in the body of the HTTP response.
  • XML-RPC = HTTP + XML + Remote Procedure Calls.
  • It is platform independent, so diverse applications can communicate with one another.
  • For example, a Java client can speak XML-RPC to a Perl server.

Question 369 – What is a Secure Webservices?

  • If we need to encrypt the data exchange, you use Secure Sockets Layer (SSL) or a Virtual Private Network to keep the bits secure.
  • For authentication, use HTTP Basic or Digest authentication with Microsoft® Windows® integration to figure out who the caller is.

Question 370 – Checklist for Webservice Performance

  • Reduce round trips.
  • Prefer message-based programming over remote procedure call (RPC) style.
  • Use primitive types for Web service parameters.
  • Avoid server state between calls.
  • Provide input validation for costly Web methods.
  • Check the caching options.
  • Check for bulk data transfer and attachments.
  • Avoid calling local Web Services.
  • Use asynchronous Web methods for I/O operations.
  • Do not use asynchronous Web methods when you depend on worker threads.
  • Consider calling Web services asynchronously when you have additional parallel work.
  • Use asynchronous invocation to call multiple unrelated Web services.
  • Call Web services asynchronously for UI responsiveness.
  • Set your proxy timeout appropriately.
  • Set your ASP.NET timeout greater than your Web service timeout.
  • Enable session state only for Web methods that need it.
  • Reduce serialization with XmlIgnore.
  • Reduce round trips.
  • Consider XML compression.

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About Author: Karthikeyan Anbarasan, Microsoft MVP (Most Valuable Professional) in ASP.NET/IIS Architecture. He is the Founder and Chief Editor of the www.f5debug.net website and has authored books on Windows Phone and Business Intelligence(SSIS). He is also a Passionate Speaker and a Blogger on Microsoft Technologies.

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