1.这个比较有效

this.Dispatcher.BeginInvoke(DispatcherPriority.Background,
(Action)(() => { Keyboard.Focus(tbReceiveMoney); }));

2.一般方式

tbReceiveMoney.Focus();

不知道为什么用下面这方法不行

tbReceiveMoney.Invoke(() =>
{
tbReceiveMoney.Focus();
});