C# 0 The Complete Reference

WebRequest.Create( )

 has two different versions. One accepts the 

URI as a string. This is the version used by the preceding programs. The other takes the URI 

as an instance of the 

Uri

 class, which is defined in the 

System

 namespace. The 

Uri

 class 

encapsulates a URI. Using 

Uri

, you can construct a URI that can be passed to 

Create( )

. You 

can also dissect a 

Uri

, obtaining its parts. Although you don’t need to use 

Uri

 for many 

simple Internet operations, you may find it valuable in more sophisticated situations.

Uri

 defines several constructors. Two commonly used ones are shown here:

public Uri(string 

uri

)

public Uri(Uri 

base

, string 

rel

)

The first form constructs a 

Uri

 given a URI in string form. The second constructs a 

Uri

 by 

adding a relative URI specified by 

rel

 to an absolute base URI specified by 

base.

 An absolute 

URI defines a complete URI. A relative URI defines only the path.

Uri

 defines many fields, properties, and methods that help you manage URIs or that give 

you access to the various parts of a URI. Of particular interest are the properties shown here:

Property

Description

public string Host { get; }

Obtains the name of the ser ver.

public string LocalPath { get; }

Obtains the local file path.

public string PathAndQuer y { get; }

Obtains the absolute path and quer y string.

public int Por t { get; }

Obtains the por t number for the specified protocol. 

For HTTP, the por t is 80.

public string Quer y { get; }

Obtains the quer y string.

public string Scheme { get; }

Obtains the protocol.

These properties are useful for breaking a URI into its constituent parts. The following 

program demonstrates their use:

// Use Uri.

using System;

using System.Net;

www.freepdf-books.com

---

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P a r t   I I :  

E x p l o r i n g   t h e   C #   L i b r a r y

class UriDemo {

  static void Main() {

    Uri sample = new Uri("http://HerbSchildt.com/somefile.txt?SomeQuery");

    Console.WriteLine("Host: " + sample.Host);

    Console.WriteLine("Port: " + sample.Port);

    Console.WriteLine("Scheme: " + sample.Scheme);

    Console.WriteLine("Local Path: " + sample.LocalPath);

    Console.WriteLine("Query: " + sample.Query);

    Console.WriteLine("Path and query: " + sample.PathAndQuery);

  }

}

The output is shown here:

Host: HerbSchildt.com

Port: 80

Scheme: http

Local Path: /somefile.txt

Query: ?SomeQuery

Path and query: /somefile.txt?SomeQuery