用Reactive Extension实现异步方法超时的操作

            Action action =  new Action(() =>
                {
                    Thread.Sleep( 5000);
                });

             var Async = Observable.FromAsyncPattern(action.BeginInvoke, action.EndInvoke);
            Observable.Timeout(Async.Invoke(), DateTimeOffset.Now.AddSeconds( 3)).ObserveOnDispatcher().Subscribe(it =>
                {
                    MessageBox.Show( " 执行完毕 ");
                }, ex =>
                    {
                        MessageBox.Show( " 超时 ");
                    });