c# HTTP Post

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