C# 0 The Complete Reference

PART II

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properties are used later in this chapter. However, for simple Internet operations, you will 

not often need to use these extra capabilities.

A Simple First Example

Internet access centers around 

WebRequest

 and 

WebResponse

. Before we examine the 

process in detail, it will be useful to see an example that illustrates the request/response 

approach to Internet access. After you see these classes in action, it is easier to understand 

why they are organized as they are.

The following program performs a simple, yet very common, Internet operation. It 

obtains the hypertext contained at a specific website. In this case, the content of McGraw-

Hill.com is obtained, but you can substitute any other website. The program displays the 

Method

Description

public vir tual void Close( )

Closes the response. It also closes 

the response stream returned by 

GetResponseStream( )

.

public vir tual Stream GetResponseStream( )

Returns an input stream connected to the 

requested URI. Using this stream, data can 

be read from the URI.

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Commonly Used Methods Defi ned by 

WebResponse

Property

Description

public vir tual long ContentLength { get; set; }

Obtains or sets the length of the content 

being received. This will be –1 if the content 

length is not available.

public vir tual string ContentType { get; set; }

Obtains or sets a description of the content.

public vir tual WebHeaderCollection

    Headers { get; }

Obtains a collection of the headers 

associated with the URI.

public vir tual bool IsFromCache { get; }

If the response came from the cache, this 

proper ty is true. It is false if the response 

was delivered over the network. 

public vir tual bool

    IsMutuallyAuthenticated { get; }

If the client and server are both authenticated, 

then this property is true. It is false otherwise. 

public vir tual Uri ResponseUri { get; }

Obtains the URI that generated the response. 

This may differ from the one requested if the 

response was redirected to another URI.

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The Proper ties Defi ned by 

WebResponse

www.freepdf-books.com

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hypertext on the screen in chunks of 400 characters, so you can see what is being received 

before it scrolls off the screen.

// Access a website.

using System;

using System.Net;

using System.IO;

class NetDemo {

  static void Main() {

    int ch;

    // First, create a WebRequest to a URI.

    HttpWebRequest req = (HttpWebRequest)

           WebRequest.Create("http://www.McGraw-Hill.com");

    // Next, send that request and return the response.

    HttpWebResponse resp = (HttpWebResponse)

           req.GetResponse();

    // From the response, obtain an input stream.

    Stream istrm = resp.GetResponseStream();

    /* Now, read and display the html present at

       the specified URI. So you can see what is

       being displayed, the data is shown

       400 characters at a time. After each 400

       characters are displayed, you must press

       ENTER to get the next 400. */

    for(int i=1; ; i++) {

      ch =  istrm.ReadByte();

      if(ch == -1) break;

      Console.Write((char) ch);

      if((i%400)==0) {

        Console.Write("\nPress Enter.");

        Console.ReadLine();

      }

    }

    // Close the response. This also closes istrm.

    resp.Close();

  }

}

The first part of the output is shown here. (Of course, over time this content will differ 

from that shown here.)

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