GetRequestStream()出现WebException错误！！

Question

this.label5.Text = "";
            this.label1.Text = "";
            this.label2.Text = "";            string urlpost = this.textBox1.Text;
            if (urlpost.IndexOf("http://") < 0) { urlpost = "http://" + urlpost; }
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(urlpost);
            request.Method = "Post";
             request.ContentType = "application/x-www-form-urlencoded";
            request.ContentLength = byteData.Length;
            try
            {                Stream requestStream = request.GetRequestStream();输入错的话的网址就会异常                requestStream.Write(byteData, 0, byteData.Length);
                requestStream.Close();
               如何去判断网址是否打开了？            }
            catch (SocketException webexception)
            {
                
                label5.Text = "网站不能打开";
                throw new WebException();
            }
            
     上面我想测试一下网址能不能打开，不知道如何判断网站是否打开了，

Answer 1

参考

判断网络地址 Url 是否存在的方法