模拟Post

   string d = "http://search.anccnet.com/searchResult2.aspx";
        //name="__VIEWSTATE"  value="/wEPDwULLTEzODQxNzY5NjNkZEc4gDy0wp5ERjILg2b7lTTH3F+w"
        //name="__EVENTVALIDATION"    value="/wEWAwKK7u6vCQLd5eLQCQLmjL2EBxmZU7jWYoh9371phOcBPCjfgdVD" 
        //name="keyword" 
        //name="gdsBtn" 
        Encoding myEncoding = Encoding.GetEncoding("gb2312");
        string param = "__VIEWSTATE=" + HttpUtility.UrlEncode("/wEPDwULLTEzODQxNzY5NjNkZEc4gDy0wp5ERjILg2b7lTTH3F+w", myEncoding)
            + "&" + "__EVENTVALIDATION=" + HttpUtility.UrlEncode("/wEWAwKK7u6vCQLd5eLQCQLmjL2EBxmZU7jWYoh9371phOcBPCjfgdVD", myEncoding)
            + "&" + "keyword=" + HttpUtility.UrlEncode("6935706000259", myEncoding)
            + "&" + "gdsBtn=" + HttpUtility.UrlEncode("111", myEncoding);

        byte[] postBytes = Encoding.ASCII.GetBytes(param);

        HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(d);
        req.Method = "POST";
        req.ContentType = "application/x-www-form-urlencoded;charset=gb2312";
        req.ContentLength = postBytes.Length;

        using (Stream reqStream = req.GetRequestStream())
        {
            reqStream.Write(postBytes, 0, postBytes.Length);
        }
        string html = "";
        using (WebResponse wr = req.GetResponse())
        {
            Stream stream = wr.GetResponseStream();
            StreamReader sr = new StreamReader(stream,System.Text.Encoding.GetEncoding("gb2312"));
             html = sr.ReadToEnd();

            //在这里对接收到的页面内容进行处理
            
        }
        Response.Write(html);

 这个也不错 http://www.cnblogs.com/oec2003/p/3322956.html