应用来电事件触发及结束通话

//注册事件
PhoneApplicationFrame frame = Application.Current.RootVisual as PhoneApplicationFrame;  //离开页面事件触发（如来电）
if (frame != null)
{
　　frame.Obscured += new EventHandler<ObscuredEventArgs>(frame_Obscured);
　　frame.Unobscured += new EventHandler(frame_Unobscured);
}