From:
http://www.c-sharpcorner.com//1/filedownloader.asp
In most cases, the WebRequest and WebResponse classes will provide all that is necessary to make the request, but when access to HTTP-specific features is required, the request or response can be typecast to HttpWebRequest or HttpWebResponse.
The HttpWebRequest and HttpWebResponse classes encapsulate a standard HTTP request and response transaction, and provide access to common HTTP headers through properties. These classes also support most of the HTTP 1.1 protocol features, including pipelining, chunking, authentication, pre-authentication, encryption, proxy support, server certificate validation, connection management, and HTTP extensions. Custom headers and headers not provided through properties can be accessed by storing them in the Headers property.
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From:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconhttp.asp
In most cases, the WebRequest and WebResponse classes provide all that is necessary to make the request, but if you need access to the HTTP-specific features exposed as properties, you can typecast these classes to HttpWebRequest or HttpWebResponse.
HttpWebRequest and HttpWebResponse encapsulate a standard HTTP request-and-response transaction and provide access to common HTTP headers. These classes also support most HTTP 1.1 features, including pipelining, chunking, authentication, preauthentication, encryption, proxy support, server certificate validation, and connection management. Custom headers and headers not provided through properties can be stored in and accessed through the Headers property.