How to: Send Data Using the WebRequest Class

How to: Send Data Using the WebRequ...

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Microsoft Visual Studio 2008/.NET Framework 3.5

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.NET Framework Developer's Guide

How to: Send Data Using the WebRequest Class

The following procedure describes the steps used to send data to a server. This procedure is commonly used to post data to a Web page.

To send data to a host server

Create a WebRequest instance by calling Create with the URI of the resource that accepts data, for example, a script or ASP .NET page.

WebRequest request = WebRequest.Create("http://www.contoso.com/");

Visual Basic

Dim request as WebRequest = WebRequest.Create("http://www.contoso.com/")

Note:
The .NET Framework provides protocol-specific classes derived from WebRequest and WebResponse for URIs that begin with "http:", "https:'', "ftp:", and "file:". To access resources using other protocols, you must implement protocol-specific classes that derive from WebRequest and WebResponse. For more information, see Programming Pluggable Protocols .

Set any property values that you need in the WebRequest. For example, to enable authentication, set the Credentials property to an instance of the NetworkCredential class.
C#
```
request.Credentials = CredentialCache.DefaultCredentials;
```
Visual Basic
```
request.Credentials = CredentialCache.DefaultCredentials
```
In most cases, the WebRequest instance itself is sufficient to send data. However, if you need to set protocol-specific properties, you must cast the WebRequest to the protocol-specific type. For example, to access the HTTP-specific properties of HttpWebRequest, cast the WebRequest to an HttpWebRequest reference. The following code example shows how to set the HTTP-specific UserAgent property.
C#
```
((HttpWebRequest)request).UserAgent = ".NET Framework Example Client";
```
Visual Basic
```
Ctype(request,HttpWebRequest).UserAgent = ".NET Framework Example Client"
```
Specify a protocol method that permits data to be sent with a request, such as the HTTP POST method.
C#
```
request.Method = "POST";
```
Visual Basic
```
request.Method = "POST"
```

Set the ContentLength property.

request.ContentLength = byteArray.Length;

Visual Basic

request.ContentLength = byteArray.Length

Set the ContentType property to an appropriate value.

request.ContentType = "application/x-www-form-urlencoded";

Visual Basic

request.ContentType = "application/x-www-form-urlencoded"

Get the stream that holds request data by calling the GetRequestStream method.

Stream dataStream = request.GetRequestStream ();

Visual Basic

Stream dataStream = request.GetRequestStream ()

Write the data to the Stream object returned by this method.

dataStream.Write (byteArray, 0, byteArray.Length);

Visual Basic

dataStream.Write (byteArray, 0, byteArray.Length)

Close the request stream by calling the Stream.Close method.
C#
```
dataStream.Close ();
```
Visual Basic
```
dataStream.Close ()
```

Send the request to the server by calling GetResponse. This method returns an object containing the server's response. The returned WebResponse object's type is determined by the scheme of the request's URI.

WebResponse response = request.GetResponse();

Visual Basic

Dim response As WebResponse = request.GetResponse()

Note:
After you are finished with a WebResponse object, you must close it by calling the Close method. Alternatively, if you have gotten the response stream from the response object, you can close the stream by calling the Stream..::.Close method. If you do not close the response or the stream, your application can run out of connections to the server and become unable to process additional requests.

You can access the properties of the WebResponse or cast the WebResponse to a protocol-specific instance to read protocol-specific properties. For example, to access the HTTP-specific properties of HttpWebResponse, cast the WebResponse to an HttpWebResponse reference.
C#
```
Console.WriteLine (((HttpWebResponse)response).StatusDescription);
```
Visual Basic
```
Console.WriteLine(CType(response, HttpWebResponse).StatusDescription)
```
To get the stream containing response data sent by the server, call the GetResponseStream method of the WebResponse.
C#
```
Stream data = response.GetResponseStream;
```
Visual Basic
```
Dim data As Stream = response.GetResponseStream
```
After reading the data from the response, you must either close the response stream using the Stream.Close method or close the response using the WebResponse.Close method. It is not necessary to call the Close method on both the response stream and the WebResponse, but doing so is not harmful.
C#
```
response.Close();
```
Visual Basic
```
response.Close()
```

Example

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

namespace Examples.System.Net
{
    public class WebRequestPostExample
    {
        public static void Main ()
        {
            // Create a request using a URL that can receive a post. 
            WebRequest request = WebRequest.Create ("http://www.contoso.com/PostAccepter.aspx ");
            // Set the Method property of the request to POST.
            request.Method = "POST";
            // Create POST data and convert it to a byte array.
            string postData = "This is a test that posts this string to a Web server.";
            byte[] byteArray = Encoding.UTF8.GetBytes (postData);
            // Set the ContentType property of the WebRequest.
            request.ContentType = "application/x-www-form-urlencoded";
            // Set the ContentLength property of the WebRequest.
            request.ContentLength = byteArray.Length;
            // Get the request stream.
            Stream dataStream = request.GetRequestStream ();
            // Write the data to the request stream.
            dataStream.Write (byteArray, 0, byteArray.Length);
            // Close the Stream object.
            dataStream.Close ();
            // Get the response.
            WebResponse response = request.GetResponse ();
            // Display the status.
            Console.WriteLine (((HttpWebResponse)response).StatusDescription);
            // Get the stream containing content returned by the server.
            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);
            // Clean up the streams.
            reader.Close ();
            dataStream.Close ();
            response.Close ();
        }
    }
}

Visual Basic

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

        Public Shared Sub Main()
            ' Create a request using a URL that can receive a post. 
            Dim request As WebRequest = WebRequest.Create("http://www.contoso.com/PostAccepter.aspx ")
            ' Set the Method property of the request to POST.
            request.Method = "POST"
            ' Create POST data and convert it to a byte array.
            Dim postData As String = "This is a test that posts this string to a Web server."
            Dim byteArray As Byte() = Encoding.UTF8.GetBytes(postData)
            ' Set the ContentType property of the WebRequest.
            request.ContentType = "application/x-www-form-urlencoded"
            ' Set the ContentLength property of the WebRequest.
            request.ContentLength = byteArray.Length
            ' Get the request stream.
            Dim dataStream As Stream = request.GetRequestStream()
            ' Write the data to the request stream.
            dataStream.Write(byteArray, 0, byteArray.Length)
            ' Close the Stream object.
            dataStream.Close()
            ' Get the response.
            Dim response As WebResponse = request.GetResponse()
            ' Display the status.
            Console.WriteLine(CType(response, HttpWebResponse).StatusDescription)
            ' Get the stream containing content returned by the server.
            dataStream = 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)
            ' Clean up the streams.
            reader.Close()
            dataStream.Close()
            response.Close()
        End Sub
    End Class
End Namespace

Tasks

How to: Request Data Using the WebRequest Class

Concepts

Creating Internet Requests

Using Streams on the Network

Accessing the Internet Through a Proxy

Requesting Data

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Post data

Kichian ... Thomas Lee | Edit | Show History

The example is a bit confusing.

In order to post data to the webpage, the postData variable must look something like:

postData = "var1=value1&var2=value2"

/Kim

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Errata

mojohead ... Thomas Lee | Edit | Show History

Step 11:
Syntax error on WebResponse.GetResponseStream() method of the WebResponse class

Should be:

Stream data = response.GetResponseStream();

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This doesn't work with MVC?

sfdrew | Edit | Show History

I tried using this approach to send a user name and password to an action for login purposes and it gets rejected and the site throws an error. Something like

http://blah.blah.com/Login/Login

The example shows sending a request to a *.aspx page, is it possible to send POST data to a an action?

Thanks
Andrew

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Post Data

leandroToledo | Edit | Show History

What i really want to know, how can I send some parameters, and these parameters enter into a field of type "textbox" then I would take the request of this consultation and analyze the data.
I can do the sample code but is doesn't solution my problem.

how I do that?

sorry english.

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