代码替换成这样再看看会出现什么!
private void button1_Click(object sender, System.EventArgs e)
{
string url="http://expert.csdn.net/member/logon.asp";
System.Net.HttpWebRequest req=(System.Net.HttpWebRequest)      System.Net.HttpWebRequest.Create(url);
req.Method="POST";//POST方式请求
req.ContentType= "application/x-www-form-urlencoded";//内容类型
//参数经过URL编码
string paraUrlCoded;
paraUrlCoded=System.Web.HttpUtility.UrlEncode("name") +"="+System.Web.HttpUtility.UrlEncode("GiantHard");
paraUrlCoded=paraUrlCoded+"&";
paraUrlCoded=paraUrlCoded+System.Web.HttpUtility.UrlEncode("pass")+"="+System.Web.HttpUtility.UrlEncode("770825"); //将URL编码后的字符串转化为字节
byte[] payload;
payload=System.Text.Encoding.UTF8.GetBytes(paraUrlCoded);
req.ContentLength=payload.Length; //设置请求的ContentLength
System.IO.Stream writer=req.GetRequestStream();//获得请求流
writer.Write(payload,0,payload.Length);//将请求参数写入流
writer.Close();//关闭请求流 //获得响应流
System.Net.HttpWebResponse response=(System.Net.HttpWebResponse)req.GetResponse();
System.IO.Stream s=response.GetResponseStream();
StreamReader reader = new StreamReader(s, Encoding.Default);
String respHTML = reader.ReadToEnd();
//显示提示内容
MessageBox.Show(respHTML, "Response Information",
MessageBoxButtons.OK,MessageBoxIcon.Exclamation);
reader.Close();
}