string url = "param1=가나다&param2=헤헤헤;

System.Net.WebRequest req = System.Net.WebRequest.Create("http://url");

byte[] param = UTF8Encoding.UTF8.GetBytes(url);

req.Method = "POST";

req.ContentType = "application/x-www-form-urlencoded; charset=UTF-8";

req.ContentLength = param.Length;

Stream stream = req.GetRequestStream();

stream.Write(param, 0, param.Length);

stream.Close();

System.Net.HttpWebResponse res =
(System.Net.HttpWebResponse)req.GetResponse();

Encoding encode;

if (res.CharacterSet.ToLower() == "utf-8") { encode = Encoding.UTF8; }

else { encode = Encoding.Default; }

Stream receive = res.GetResponseStream();

StreamReader reader = new StreamReader(receive, encode);

string resultText = reader.ReadToEnd();

reader.Close();

receive.Close();

res.Close();