Generic Request/Response Architecture
The request/response architecture
is based on Uniform Resource
Indicator (URI) and stream I/O, follows the factory design pattern,
and makes good use of abstract types and interfaces. A factory
method, WebRequest.Create( ), parses the URI and creates the appropriate protocol
handler to fulfill the request.
Protocol handlers share a common abstract base type
(WebRequest), which exposes properties that
configure the request and methods used to retrieve the response.
Responses are also represented as types and share a common abstract
base type (WebResponse), which exposes a
NetworkStream, providing a simple streams-based
I/O and easy integration into the rest of the FCL.
This example is a simple implementation of the popular Unix snarf
utility. It demonstrates the use of the WebRequest
and WebResponse classes to retrieve the contents
of a URI and print them to the console:
// Snarf.cs // Run Snarf.exe <http-uri> to retrieve a web page // e.g. snarf.exe http://www.oreilly.com/catalog/csharpnut/ using System; using System.IO; using System.Net; using System.Text; class Snarf { static void Main(string[ ] args) { // Retrieve the data at the URL with a WebRequest instance WebRequest req = WebRequest.Create(args[0]); WebResponse resp = req.GetResponse( ); // Read in the data, performing ASCII->Unicode encoding Stream s = resp.GetResponseStream( ); StreamReader sr = new StreamReader(s, Encoding.ASCII); string doc = sr.ReadToEnd( ); Console.WriteLine(doc); ...