WebClient post时 HTTP 500错误问题

[火鸟李国平]

访问一个需要登录的网站,所以我就post东西给他,从他的页面中知道了他有四个数据,结果post时HTTP500错误
private void button2_Click(object sender, System.EventArgs e)
{
try
{

string uriString="http://www.tyue.com/soft/chklogin.asp";
WebClient myWebClient = new WebClient();
NameValueCollection myNameValueCollection = new NameValueCollection();
myNameValueCollection.Add("user","xxxx");
myNameValueCollection.Add("password","xxxx");
myNameValueCollection.Add("cookiesdate","1");
myNameValueCollection.Add("Submit","登录");
myWebClient.BaseAddress="http://www.tyue.com/soft/default.asp";

byte[] responseArray = myWebClient.UploadValues(uriString,"post",myNameValueCollection);//结果到这儿就报错了,http 500
textBox2.Text =Encoding.ASCII.GetString(responseArray);

Stream myStream = myWebClient.OpenRead(textBox1.Text);
StreamReader sr = new StreamReader(myStream,Encoding.Default );
textBox2.Text=sr.ReadToEnd();
myStream.Close();
}
catch (Exception ee)



{
throw (ee);


}

}