C# MultiThreaded MultiProxy Support browser?

sing System;
using System.Net;
using System.Net.Security;
using System.Security.Cryptography.X509Certificates;


namespace Utility
{
    public class WebClientEx : WebClient
    {
        static WebClientEx()
        {
            ServicePointManager.Expect100Continue = false;
            ServicePointManager.ServerCertificateValidationCallback = (RemoteCertificateValidationCallback)((object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors) => true);
            ServicePointManager.DefaultConnectionLimit = 1000;
        }


        public WebClientEx()
            : base()
        {
            this.AllowAutoRedirect = true;
            this.Cookies = new CookieContainer();
        }


        protected override WebRequest GetWebRequest(Uri address)
        {
            HttpWebRequest request = base.GetWebRequest(address) as HttpWebRequest;
            if (request.Method == "POST")
            {
                request.ContentType = "application/x-www-form-urlencoded";
            }
            request.AutomaticDecompression = DecompressionMethods.GZip;
            request.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.12) Gecko/20101026 Firefox/3.6.12";
            request.CookieContainer = this.Cookies;
            request.AllowAutoRedirect = this.AllowAutoRedirect;
            request.Timeout = 10000;
            return request;
        }


        public bool AllowAutoRedirect { get; set; }
        public CookieContainer Cookies { get; set; }
    }
}