C#: How to post data to a web page using WebRequest Class

This afternoon, a user from yahoo answer ask me on how to send xml data to a web page using C#. He want his client application to post updates on a web application that accepts uniform XML format. My advice to him is to use the .NET's WebRequest class. WebRequest is an 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 you client application to a particular URI (Uniform Resource Identifier), 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.

Here's the steps to send data to a server. This method is commonly used to post data to a Web page:

1. Create a WebRequest instance by calling Create with the URI of the resource that accepts data

string uri = "http://127.0.0.1/webmsgbroker/default.aspx";
WebRequest req = WebRequest.Create(uri);

2. Specify the protocol method and the content type to use in sending the request

req.Method = "POST";
req.ContentType = "text/xml";

3. Wrap the request stream with a text-based writer

StreamWriter writer = new StreamWriter(req.GetRequestStream());
// Write the xml text into the stream, GetTextFromXMLFile is a custom function the convert XML to stream
writer.WriteLine(this.GetTextFromXMLFile("C:/test.xml"));
writer.Close();

4. Send the data to the webserver and wait for the response.

rsp = req.GetResponse();

Here is the complete sample sourcecode:

//Function to convert XML to stream
private string GetTextFromXMLFile(string file)
{
StreamReader reader = new StreamReader(file);
string ret = reader.ReadToEnd();
reader.Close();
return ret;
}

//Button to Post data to web page
private void button1_Click(object sender, EventArgs e)
{
WebRequest req = null;
WebResponse rsp = null;

try
{
//URL of message broker
string uri = "http://127.0.0.1/webmsgbroker/default.aspx";
req = WebRequest.Create(uri);
req.Proxy = wproxy;
req.Method = "POST"; // Post method
req.ContentType = "text/xml"; // content type
// Wrap the request stream with a text-based writer
StreamWriter writer = new StreamWriter(req.GetRequestStream());
// Write the xml text into the stream
string fileName = "C:/test.xml";
writer.WriteLine(this.GetTextFromXMLFile(@fileName));
writer.Close();
// Send the data to the webserver
rsp = req.GetResponse();

}
catch (WebException webEx)
{
MessageBox.Show(webEx.Message);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
finally
{
if (req != null) req.GetRequestStream().Close();
if (rsp != null) rsp.GetResponseStream().Close();
}
}

Related Topic:
How to create ASP.NET web service in .NET
How to consume web services

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