C# 4 and .NET 4

Utility Classes ❘ 653
System.Object
System.MarshalByRefObject
System.Net.WebRequest
System.Net.WebResponse
System.Net.HttpWebRequest
System.Net.FileWebRequest
System.Net.FtpWebRequest
System.Net.HttpWebResponse
System.Net.FileWebResponse
System.Net.FtpWebResponse
Third-Party Web
Request Classes
figure 24-9
Third-Party Web
Response Classes
The fact that you need an object specifically capable of dealing with the HTTP protocol is clear from the
URI that you supply to WebRequest.Create(). WebRequest.Create() examines the protocol specifier in
the URI to instantiate and return an object of the appropriate class. This keeps your code free from having
to know anything about the derived classes or specific protocol used. When you need to access specific
features of a protocol, you might need the properties and methods of the derived class, in which case you
can cast your WebRequest or WebResponse reference to the derived class.
With this architecture, you should be able to send requests using any of the common protocols. However,
Microsoft currently provides derived classes to cover only the HTTP, HTTPS, FTP, and FILE protocols.
The FTP option is the latest option provided by the .NET Framework (ever since the release of the .NET
Framework 2.0). If you want to utilize other protocols, for example SMTP, then you need to use the
Windows Communication Foundation, revert to using the Windows API, or use the SmtpClient object.
uTiliTy Classes
This section covers a couple of utility classes to make web programming easier when dealing with URIs and
IP addresses.
uris
Uri and UriBuilder are two classes in the System (not System.Net) namespace, and they are both
intended to represent a URI. UriBuilder allows you to build a URI given the strings for the component
parts, and the Uri class allows you to parse, combine, and compare URIs.
For the Uri class, the constructor requires a completed URI string:
Uri MSPage = new
Uri("http://www.Microsoft.com/SomeFolder/SomeFile.htmOrder=true");
The class exposes a large number of read-only properties. A Uri object is not intended to be modified after
it has been constructed:
string Query = MSPage.Query;
string AbsolutePath = MSPage.AbsolutePath;
string Scheme = MSPage.Scheme;
int Port = MSPage.Port;
string Host = MSPage.Host;
bool IsDefaultPort = MSPage.IsDefaultPort;
// Order=true;
// /SomeFolder/SomeFile.htm
// http
// 80 (the default for http)
// www.microsoft.com
// true since 80 is default
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