WebRequest Class (System.Net)

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Microsoft Visual Studio 2008/.NET Framework 3.5

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.NET Framework Class Library

WebRequest Class

Makes a request to a Uniform Resource Identifier (URI). This is an abstract class.

Namespace: System.Net
Assembly: System (in System.dll)

Syntax

Visual Basic (Declaration)

<SerializableAttribute> _
Public MustInherit Class WebRequest _
    Inherits MarshalByRefObject _
    Implements ISerializable

Visual Basic (Usage)

Dim instance As WebRequest

[SerializableAttribute]
public abstract class WebRequest : MarshalByRefObject, 
    ISerializable

Visual C++

[SerializableAttribute]
public ref class WebRequest abstract : public MarshalByRefObject, 
    ISerializable

JScript

public abstract class WebRequest extends MarshalByRefObject implements ISerializable

Remarks

WebRequest is the abstract base class for the .NET Framework's request/response model for accessing data from the Internet. An application that uses the request/response model can request data from the Internet in a protocol-agnostic manner, in which the application works with instances of the WebRequest class while protocol-specific descendant classes carry out the details of the request.

Requests are sent from an application to a particular URI, such as a Web page on a server. The URI determines the proper descendant class to create from a list of WebRequest descendants registered for the application. WebRequest descendants are typically registered to handle a specific protocol, such as HTTP or FTP, but can be registered to handle a request to a specific server or path on a server.

The WebRequest class throws a WebException when errors occur while accessing an Internet resource. The Status property is one of the WebExceptionStatus values that indicates the source of the error. When Status is WebExceptionStatus..::.ProtocolError, the Response property contains the WebResponse received from the Internet resource.

Because the WebRequest class is an abstract class, the actual behavior of WebRequest instances at run time is determined by the descendant class returned by Create method. For more information about default values and exceptions, see the documentation for the descendant classes, such as HttpWebRequest and FileWebRequest.

Note:
Use the Create method to initialize new WebRequest instances. Do not use the WebRequest constructor.

Note:
If the application that creates the WebRequest object runs with the credentials of a Normal user, the application will not be able to access certificates installed in the local machine store unless permission has been explicitly given to the user to do so.

Notes to Inheritors:

When you inherit from WebRequest, you must override the following members: Method, RequestUri, Headers, ContentLength, ContentType, Credentials, PreAuthenticate, GetRequestStream, BeginGetRequestStream, EndGetRequestStream, GetResponse, BeginGetResponse, and EndGetResponse. In addition, you must provide an implementation of the IWebRequestCreate interface, which defines the Create method used when you call Create. You must register the class that implements the IWebRequestCreate interface, using the RegisterPrefix method or the configuration file.

Examples

The following example shows how to create a WebRequest instance and return the response.

Visual Basic

Imports System
Imports System.IO
Imports System.Net
Imports System.Text
Namespace Examples.System.Net
    Public Class WebRequestGetExample

        Public Shared Sub Main()
            ' Create a request for the URL.         
            Dim request As WebRequest = WebRequest.Create("http://www.contoso.com/default.html")
            ' If required by the server, set the credentials.
            request.Credentials = CredentialCache.DefaultCredentials
            ' Get the response.
            Dim response As HttpWebResponse = CType(request.GetResponse(), HttpWebResponse)
            ' Display the status.
            Console.WriteLine(response.StatusDescription)
            ' Get the stream containing content returned by the server.
            Dim dataStream As Stream = response.GetResponseStream()
            ' Open the stream using a StreamReader for easy access.
            Dim reader As New StreamReader(dataStream)
            ' Read the content.
            Dim responseFromServer As String = reader.ReadToEnd()
            ' Display the content.
            Console.WriteLine(responseFromServer)
            ' Cleanup the streams and the response.
            reader.Close()
            dataStream.Close()
            response.Close()
        End Sub 'Main
    End Class 'WebRequestGetExample
End Namespace

using System;
using System.IO;
using System.Net;
using System.Text;

namespace Examples.System.Net
{
    public class WebRequestGetExample
    {
        public static void Main ()
        {
            // Create a request for the URL.         
            WebRequest request = WebRequest.Create ("http://www.contoso.com/default.html");
            // If required by the server, set the credentials.
            request.Credentials = CredentialCache.DefaultCredentials;
            // Get the response.
            HttpWebResponse response = (HttpWebResponse)request.GetResponse ();
            // Display the status.
            Console.WriteLine (response.StatusDescription);
            // Get the stream containing content returned by the server.
            Stream dataStream = response.GetResponseStream ();
            // Open the stream using a StreamReader for easy access.
            StreamReader reader = new StreamReader (dataStream);
            // Read the content.
            string responseFromServer = reader.ReadToEnd ();
            // Display the content.
            Console.WriteLine (responseFromServer);
            // Cleanup the streams and the response.
            reader.Close ();
            dataStream.Close ();
            response.Close ();
        }
    }
}

Visual C++

#using <System.dll>

using namespace System;
using namespace System::IO;
using namespace System::Net;
using namespace System::Text;
int main()
{

   // Create a request for the URL.   
   WebRequest^ request = WebRequest::Create( "http://www.contoso.com/default.html" );

   // If required by the server, set the credentials.
   request->Credentials = CredentialCache::DefaultCredentials;

   // Get the response.
   HttpWebResponse^ response = dynamic_cast<HttpWebResponse^>(request->GetResponse());

   // Display the status.
   Console::WriteLine( response->StatusDescription );

   // Get the stream containing content returned by the server.
   Stream^ dataStream = response->GetResponseStream();

   // Open the stream using a StreamReader for easy access.
   StreamReader^ reader = gcnew StreamReader( dataStream );

   // Read the content.
   String^ responseFromServer = reader->ReadToEnd();

   // Display the content.
   Console::WriteLine( responseFromServer );

   // Cleanup the streams and the response.
   reader->Close();
   dataStream->Close();
   response->Close();
}

.NET Framework Security

WebPermission
To access the requested URI or any URI that the request is redirected to. Associated enumeration: Connect.

Inheritance Hierarchy

System..::.Object
  System..::.MarshalByRefObject
    System.Net..::.WebRequest
      System.IO.Packaging..::.PackWebRequest
      System.Net..::.FileWebRequest
      System.Net..::.FtpWebRequest
      System.Net..::.HttpWebRequest

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

Reference

WebRequest Members

System.Net Namespace

HttpWebRequest

Other Resources

Requesting Data

Programming Pluggable Protocols