ASCIIEncoding encoding = new ASCIIEncoding();
string post_url = "http://172.16.24.44/postdata.php";
string poststring = "monkeys=blue\&trousers=black";
byte[] data = encoding.GetBytes(poststring);

HttpWebRequest httpRequest = (HttpWebRequest)WebRequest.Create(post_url);
httpRequest.Method = "POST";
httpRequest.ContentType="application/x-www-form-urlencoded";
httpRequest.ContentLength = data.Length;
Stream newStream=httpRequest.GetRequestStream();
newStream.Write(data,0,data.Length);
newStream.Close();

HttpWebResponse response = (HttpWebResponse)httpRequest.GetResponse ();
Stream receiveStream = response.GetResponseStream ();
StreamReader readStream = new StreamReader (receiveStream);
textBox1.Text = "Response stream received.";
textBox1.Text = readStream.ReadToEnd().Replace("\\n","\\r\\n");
response.Close ();
readStream.Close ();