C# in a Nutshell

Chapter 33. System.Net

System.Net supports a high-level API for working with common Internet protocols (HTTP being the principal example) without having to deal with low-level details (such as the actual protocol format). In addition, this namespace provides some high-level constructs for working with networks — TCP/IP in particular.

Most C# programmers will work with either the WebClient type, which provides the most high-level view of doing HTTP-style request/response communications over a TCP/IP network (such as the Internet), or else the slightly lower-level WebRequest and WebResponse types. The choice between the two is really not all that difficult—for most high-level, protocol-agnostic work, WebClient will likely be the preferred choice. If protocol-specific actions need to be taken (such as specifying additional headers as part of an HTTP request, for example), then likely the C# programmer will want to work with WebRequest and WebResponse. To be specific, the C# programmer will work with the concrete derived types HttpWebRequest and HttpWebResponse.

As shipped, the .NET Framework Class Library provides implementations for three URI protocol schemes: HTTP, HTTPS, and files (http:, https: and file:, respectively). For support of other URI types (such as FTP, NNTP, or POP3), a new derivative of WebRequest and WebResponse must be written, an Abstract Factory type implementing the IWebRequestCreate interface must be created, and an instance of it (along with the protocol ...