public partial class UserControl1 : UserControl, IObjectSafety
    {
        //检测网络状态
        [DllImport("wininet.dll")]
        private extern static bool InternetGetConnectedState(out int connectionDescription, int reservedValue);
        /// <summary>
        /// 检测网络状态
        /// </summary>
        private bool isConnected()
        {
            int I = 0;
            bool state = InternetGetConnectedState(out I, 0);
            return state;
        }
 　　　　private void update_Load(object sender, EventArgs e)
        {
            if (isConnected())
            {
            //network  is connected.
            }
            else
            {
             //network is not connected.
             }

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