Web.cs

using System;
using System.IO;
using System.Net;
using System.Text;

class Web
{
    public static string GetPost(string Url, params string[] postdata)
    {
        string result = string.Empty;
        string data = string.Empty;

        System.Text.ASCIIEncoding ascii = new ASCIIEncoding();

        if (postdata.Length % 2 != 0)
        {
            return "Parameters must be even , \"user\" , \"value\" , ... etc";
        }

        for (int i = 0; i < postdata.Length; i += 2)
        {
            data += string.Format("&{0}={1}", postdata[i], postdata[i + 1]);
        }

        data = data.Remove(0, 1);

        byte[] bytesarr = ascii.GetBytes(data);
        try
        {
            WebRequest request = WebRequest.Create(Url);

            request.Method = "POST";
            request.ContentType = "application/x-www-form-urlencoded";
            request.ContentLength = bytesarr.Length;

            System.IO.Stream streamwriter = request.GetRequestStream();
            streamwriter.Write(bytesarr, 0, bytesarr.Length);
            streamwriter.Close();

            WebResponse response = request.GetResponse();
            streamwriter = response.GetResponseStream();

            System.IO.StreamReader streamread = new System.IO.StreamReader(streamwriter);
            result = streamread.ReadToEnd();
            streamread.Close();
        }
        catch (Exception ex)
        {
            return ex.Message;
        }
        return result;
    }
}