bool bolPing = true;//标识量

            System.Net.NetworkInformation.Ping ping = new System.Net.NetworkInformation.Ping();
            System.Net.NetworkInformation.PingReply pingReply = ping.Send(System.Net.IPAddress.Parse("202.108.22.5"), 500);//Ping百度，500毫秒超时
            //判断ping返回来的结果
            bolPing = (pingReply.Status == System.Net.NetworkInformation.IPStatus.Success);


            if (bolPing)
            {
                MessageBox.Show("网络连接正常");
            }

[DllImport("wininet.dll")]
        private extern static bool InternetGetConnectedState(int Description, int ReservedValue);


        private void button1_Click(object sender, EventArgs e)
        {
            bool bolConnect = true;

            int Desc = 0;
            bolConnect = InternetGetConnectedState(Desc, 0);


            if (bolConnect)
            {
                MessageBox.Show("网络连接正常");
            }
        }