100分啦，想要的进来

用HttpWebRequest类，下面这个例子发了一个Request, 并且显示收到数据的大小。虽然是Console的，但是和Winform的一样。class MainApp
{
   static void Main()
   {
      HttpWebRequest request;
      IAsyncResult ar;      request = (HttpWebRequest)WebRequest.CreateDefault(
         new Uri("http://www.microsoft.com"));
      ar = request.BeginGetResponse(new AsyncCallback(PoolFunc), request);
      Console.WriteLine("Synchronous: {0}", ar.CompletedSynchronously);
      Console.ReadLine();
   }
   static void PoolFunc(IAsyncResult ar)
   {
      HttpWebRequest request;
      HttpWebResponse response;      Console.WriteLine("Response received on pool: {0}",
         Thread.CurrentThread.IsThreadPoolThread);
      request = (HttpWebRequest)ar.AsyncState;
      response = (HttpWebResponse)request.EndGetResponse(ar);
      Console.WriteLine("  Response size: {0}",
         response.ContentLength);
   }
}