using System.Net;
...
string HttpPost (string uri, string parameters)
{
// parameters: name1=value1&name2=value2    
WebRequest webRequest = WebRequest.Create (uri);
//string ProxyString =
// System.Configuration.ConfigurationManager.AppSettings
// [GetConfigKey("proxy")];
//webRequest.Proxy = new WebProxy (ProxyString, true);
//Commenting out above required change to App.Config
webRequest.ContentType = "application/x-www-form-urlencoded";
webRequest.Method = "POST";
byte[] bytes = Encoding.ASCII.GetBytes (parameters);
Stream os = null;
try
{ // send the Post
webRequest.ContentLength = bytes.Length; //Count bytes to send
os = webRequest.GetRequestStream();
os.Write (bytes, 0, bytes.Length); //Send it
}
catch (WebException ex)
{
MessageBox.Show ( ex.Message, "HttpPost: Request error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
finally
{
if (os != null)
{
os.Close();
}
}

try
{ // get the response
WebResponse webResponse = webRequest.GetResponse();
if (webResponse == null)
{ return null; }
StreamReader sr = new StreamReader (webResponse.GetResponseStream());
return sr.ReadToEnd ().Trim ();
}
catch (WebException ex)
{
MessageBox.Show ( ex.Message, "HttpPost: Response error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
return null;
} // end HttpPost