/// <summary>
 /// 设备状态改变事件
 /// </summary>
 /// <param name="dev"></param>
 /// <param name="isOnline"></param>
 private void DeviceMonitor_OnDeviceConnected(Domains.IDevice dev, bool isOnline)
 {
     SystemContext.Instance.AsyncOperation.Post(t =>
     {
         if (isOnline)
         {
             Devices.Add(dev);
         }
         else
         {
             Devices.Remove(dev);
         }
     }, null);
 }
 /// <summary>
 /// 设备状态改变事件
 /// </summary>
 /// <param name="dev"></param>
 /// <param name="isOnline"></param>
 private void DeviceMonitor_OnDeviceConnected(Domains.IDevice dev, bool isOnline)
 {
     SystemContext.Instance.AsyncOperation.Post(t =>
     {
         if (isOnline)
         {
             Devices.Add(dev);
         }
         else
         {
             Devices.Remove(Devices.FirstOrDefault(d => d.Equals(dev)));
         }
         HasDevice = Devices.Count > 0;
     }, null);
 }