//判断网络连接
        [DllImport("wininet")]
        private extern static bool InternetGetConnectedState(out int connectionDescription, int reservedValue);
        ///<summary>
        /// 检测本机的网络连接
        ///</summary> 
       private void button1_Click(object sender, EventArgs e)
        {
            //判断是否联网
                int i = 0;
                if (InternetGetConnectedState(out i, 0))
                {
                    //联网
                    MessageBox.Show("Thylx提醒您：你的计算机已连接到网络上！");
                 }
                 else
                  {
                     //断网
                     MessageBox.Show("Thylx提醒您：本地连接已断开！");
                  }
        }