private void OnRotationChanged(float oldRotation, float newRotation)
 {
     if (RotationChanged != null)
     {
         RotationEventArgs args = new RotationEventArgs(oldRotation, newRotation);
         RotationChanged(this, args);
     }
 }
 void bt_RotationEvent(object sender, RotationEventArgs e)
 {
     try
     {
         if (lblTime.InvokeRequired)
         {
             lblTime.Invoke(new EventHandler(delegate { lblTime.Text = e.Time; }));
         }
         else
         {
             lblTime.Text = e.Time;
         }
     }
     catch { }
 }