1、

//===========獲取計算機上網的公網ip:113.57.68.117 
protected void Button2_Click(object sender, EventArgs e)
        {                       
           try
            {
                //string ip = "";

                WebClient MyWebClient = new WebClient();
                MyWebClient.Credentials = CredentialCache.DefaultCredentials;//獲取或設定用於向Internet資源的請求進行身份驗證的網路憑據

                Byte[] pageData = MyWebClient.DownloadData("http://www.net.cn/static/customercare/yourip.asp"); //從指定網站下載資料

                string pageHtml = Encoding.Default.GetString(pageData);  //如果獲取網站頁面採用的是GB2312，則使用這句


                //string pageHtml = Encoding.UTF8.GetString(pageData); //如果獲取網站頁面採用的是UTF-8，則使用這句

                //string[] str = HtmlHelper.GetElementsByTagName(pageHtml, "h2");

                // string[] str1 = str[0].Replace("<h2>", "").Split(',');
                //ip = str1[0];
                // Response.Write(ip);

                string s = GetStr(pageHtml, "<h2>", "</h2>");
                Response.Write(s);

            }
            catch (WebException webEx)
            {
                webEx.Message.ToString();
            }
        }

        public string GetStr(string Content, string start, string end)
        {
            var posStart = Content.IndexOf(start);
            var posEnd = Content.IndexOf(end);
            return Content.Substring(posStart, (posEnd - posStart + end.Length));
        }


//===========獲取ip和地理資訊 
        protected void Button1_Click(object sender, EventArgs e)
        {
            //獲取ip和地理資訊
            string url = "http://pv.sohu.com/cityjson";
            WebRequest wRequest = WebRequest.Create(url);
            wRequest.Method = "GET";
            wRequest.ContentType = "text/html;charset=UTF-8";
            WebResponse wResponse = wRequest.GetResponse();
            Stream stream = wResponse.GetResponseStream();
            StreamReader reader = new StreamReader(stream, System.Text.Encoding.Default);
            string str = reader.ReadToEnd();   //url返回的值  

            reader.Close();
            wResponse.Close();
            //var returnCitySN = {"cip": "113.57.68.117", "cid": "420100", "cname": "湖北省武漢市"};
           // Response.Write(str);

            var start = str.IndexOf('{');
            var end = str.IndexOf('}');

            str = str.Substring(start, (end - start) + 1);
            //{"cip": "113.57.68.117", "cid": "420100", "cname": "湖北省武漢市"}
            //Response.Write(str);

            //湖北省武漢市
            JObject jonObj = JObject.Parse(str);
            Response.Write(jonObj["cname"].ToString() + "  " + jonObj["cip"].ToString());
        }