string url = @"https://www.nix.ru/";
HttpWebRequest WebRequest = (HttpWebRequest)System.Net.WebRequest.Create(url);
WebRequest.Method = "GET";
 //WebRequest.Proxy = new WebProxy(ProxyURI, true, null, null);
using (HttpWebResponse httpWebResponse = (HttpWebResponse)WebRequest.GetResponse())
      {
          using (Stream stream = httpWebResponse.GetResponseStream())
          {
              if (stream != null)
                 {
                   using (StreamReader reader = new StreamReader(stream, Encoding.GetEncoding(httpWebResponse.CharacterSet)))
                    {   return reader.ReadToEnd();   }
                  }
               return "False";
          }
      }