Makes a request to a Uniform Resource Identifier (URI). This is an
abstract class.
Namespace: System.Net
Assembly: System (in system.dll)
Visual Basic (Declaration)
<SerializableAttribute> _
Public MustInherit Class WebRequest
Inherits MarshalByRefObject
Implements ISerializable
Dim instance As WebRequest
[SerializableAttribute]
public abstract class WebRequest : MarshalByRefObject, ISerializable
[SerializableAttribute]
public ref class WebRequest abstract : public MarshalByRefObject, ISerializable
/** @attribute SerializableAttribute() */
public abstract class WebRequest extends MarshalByRefObject implements ISerializable
SerializableAttribute
public abstract class WebRequest extends MarshalByRefObject implements ISerializable
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 WebException.Status property is one of the WebExceptionStatus values that indicates the source of the error. When WebException.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 System.Net.WebRequest.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.
The following example shows how to create a WebRequest instance and return the response.
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 ();
}
}
}
#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();
}
- WebPermission
To access the requested URI or any URI that the request is redirected to. Associated enumeration: Connect.
System.Object
System.MarshalByRefObject
System.Net.WebRequest
System.Net.FileWebRequest
System.Net.FtpWebRequest
System.Net.HttpWebRequest
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.
.NET Framework
Supported in: 2.0, 1.1, 1.0
.NET Compact Framework
Supported in: 2.0, 1.0