HtmlElement ClickBtn =null;
if (e.Url.ToString().ToLower().IndexOf("xxx.htm") > 0) //登陆页面
{
  HtmlDocument doc = webBrowser1.Document;
  for (int i = 0; i < doc.All.Count ; i++)
  {
   if (doc.All[i].TagName.ToUpper().Equals("INPUT"))
   {
    switch (doc.All[i].Name)
    {
     case "userCtl":
      doc.All[i].InnerText = "user01";
      break;
     case "passCt1":
      doc.All[i].InnerText = "mypass";
      break;
     case "B1":
      ClickBtn = doc.All[i]; //提交按钮
      break;
    }
   }
  }
  ClickBtn.InvokeMember("Click"); //执行按扭操作
}

private void StartLoop(int ProxyNum)
{
 WebClient [] wcArray = new WebClient[ProxyNum]; //初始化
 for (int idArray = 0; idArray< ProxyNum;idArray++)
 {
  wcArray[idArray] = new WebClient();
  wcArray[idArray].OpenReadCompleted += new OpenReadCompletedEventHandler(Pic_OpenReadCompleted2);
  wcArray[idArray].UploadDataCompleted += new UploadDataCompletedEventHandler(Pic_UploadDataCompleted2);
  try
  {
   ......
   wcArray[idArray].Proxy = new WebProxy(proxy[1], port);
   wcArray[idArray].OpenReadAsync(new Uri("http://xxxx.com.cn/tp.asp?Id=129")); //打开WEB;
   proxy = null;
  }
  catch
  {
  }
 }
}
private void Pic_OpenReadCompleted2(object sender, OpenReadCompletedEventArgs e)
{
  if (e.Error == null)
  {
     string textData = new StreamReader(e.Result, Encoding.Default).ReadToEnd(); //取返回信息
     .....
     String cookie = ((WebClient)sender).ResponseHeaders["Set-Cookie"];
     ((WebClient)sender).Headers.Add("Content-Type", "application/x-www-form-urlencoded");
     ((WebClient)sender).Headers.Add("Accept-Language", "zh-cn");
     ((WebClient)sender).Headers.Add("Cookie", cookie);
     string postData = "......"
     byte[] byteArray = Encoding.UTF8.GetBytes(postData); // 转化成二进制数组 
     ((WebClient)sender).UploadDataAsync(new Uri("http://xxxxxxy.com.cn/tp.asp?Id=129"), "POST", byteArray);
  }
}
private void Pic_UploadDataCompleted2(object sender, UploadDataCompletedEventArgs e)
{
  if (e.Error == null)
  {
   string returnMessage = Encoding.Default.GetString(e.Result);
   ......
  }
}

private bool PostWebRequest()  
{
   CookieContainer cc = new CookieContainer();
   string pos tData = "user=" + strUser + "&pass=" + strPsd;
   byte[] byteArray = Encoding.UTF8.GetBytes(postData); // 转化
   HttpWebRequest webRequest2 = (HttpWebRequest)WebRequest.Create(new Uri("http://www.xxxx.com/chk.asp"));
   webRequest2.CookieContainer = cc;
   webRequest2.Method = "POST";
   webRequest2.ContentType = "application/x-www-form-urlencoded";
   webRequest2.ContentLength = byteArray.Length;
   Stream newStream = webRequest2.GetRequestStream();
   // Send the data.
   newStream.Write(byteArray, 0, byteArray.Length); //写入参数
   newStream.Close();
   HttpWebResponse response2 = (HttpWebResponse)webRequest2.GetResponse();
   StreamReader sr2=new StreamReader(response2.GetResponseStream(), Encoding.Default);
   string text2 = sr2.ReadToEnd();
   ......
}

WebRequest request = WebRequest.Create(Url);
request.Method = "POST";
request.Timeout = 100000;
request.GetRequestStream().Close();
WebResponse response = request.GetResponse();
StreamReader sr = new StreamReader(response.GetResponseStream(), System.Text.Encoding.UTF8);
webInfo = sr.ReadToEnd();
sr.Close();