protected void Button1_Click(object sender, EventArgs e)
    {
     string ip="";
        if (Request.ServerVariables["HTTP_VIA"] != null)
        {
            ip = Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
        }
        else
        {
            ip = Request.ServerVariables["REMOTE_ADDR"].ToString();
        }
        TextBox1.Text = userIP;
    }

 /// <summary>
        /// 获取局域网IP
        /// </summary>
        /// <returns></returns>
        public static string GetLocalhostIpAddress()
        {
            string localhostIp = "";
            localhostIp = Dns.GetHostEntry(Dns.GetHostName()).AddressList[0].ToString();
            return localhostIp;
        }