string requestUri = "<http://www.example.com>";
string requestBodyString = "Request body string.";
string contentType = "text/plain";
string requestMethod = "POST";

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(requestUri)
{
  Method = requestMethod,
  ContentType = contentType,
};

byte[] bytes = Encoding.UTF8.GetBytes(requestBodyString);
Stream stream = request.GetRequestStream();
stream.Write(bytes, 0, bytes.Length);
stream.Close();

HttpWebResponse response = (HttpWebResponse)request.GetResponse();