9.3 HTTP-Specific Support

The request/response architecture inherently supports protocol-specific extensions via the use of subtyping. Since WebRequest.Create( ) creates and returns the appropriate handler type based on the URI, accessing protocol-specific features is as easy as downcasting the returned WebRequest object to the appropriate protocol-specific handler and accessing the extended functionality.

The FCL includes specific support for the HTTP protocol, including the ability to easily access and control elements of an interactive web session, such as the HTTP headers, user-agent strings, proxy support, user credentials, authentication, keep-alives, pipelining, and more.

This example demonstrates the use of the HTTP-specific request/response classes to control the user-agent string for the request and retrieve the server type:

 // ProbeSvr.cs // Run ProbeSvr.exe <servername> to retrieve the server type using System; using System.Net; class ProbeSvr {   static void Main(string[ ] args) {        // Get instance of WebRequest ABC, convert to HttpWebRequest     WebRequest req = WebRequest.Create(args[0]);     req.Method = "HEAD"; // we're just looking at headers     HttpWebRequest httpReq = (HttpWebRequest)req;        // Access HTTP-specific features such as User-Agent     httpReq.UserAgent = "CSPRProbe/1.0";        // Retrieve response and print to console     WebResponse resp = req.GetResponse( );     HttpWebResponse httpResp = (HttpWebResponse)resp;     Console.WriteLine(httpResp.Server);   } } 


C# in a Nutshell
C # in a Nutshell, Second Edition
ISBN: 0596005261
EAN: 2147483647
Year: 2005
Pages: 963

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