string url="";
string param="";
string result = string.Empty;
HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(url);
Encoding encoding = Encoding.UTF8;
byte[] bs = Encoding.UTF8.GetBytes(param);
string responseData = String.Empty;
req.Method = "Post";
req.Accept = "application/json, text/javascript, */*; q=0.01";
req.ContentType = "application/json; charset=UTF-8";
using (Stream reqStream = req.GetRequestStream())
{
    reqStream.Write(bs, 0, bs.Length);
    reqStream.Close();
}
using (HttpWebResponse response = (HttpWebResponse)req.GetResponse())
{
    using (StreamReader reader = new StreamReader(response.GetResponseStream(), encoding))
    {
        responseData = reader.ReadToEnd().ToString();
    }
    result = responseData;
}