问题描述
我已经看到了跨线程访问GUI控件的常见设置，如下所述：
I've seen the common setup for cross threading access to a GUI control, such as discussed here:Shortest way to write a thread-safe access method to a windows forms control
我发现的所有网页点击都会描述类似的东西。
All the web hits I found describe a similar thing.
然而，为什么我们需要检查InvokeRequired？我们不能直接调用Invoke？
However, why do we need to check InvokeRequired? Can't we just call Invoke directly?
我假设答案是否定的，所以我真正的问题是为什么？
I assume the answer is no, so my real question is 'why'?
推荐答案
从非UI线程我们不能触摸UI - 非常糟糕的事情可能发生，因为控件具有线程关联性。所以从非UI线程我们必须（最小）调用调用或 BeginInvoke 。
From non-UI threads we can't touch the UI - very bad things can happen, since controls have thread affinity. So from a non-UI thread we must (at a minumum) call Invoke or BeginInvoke.
然而，对于UI线程，我们不要要调用调用很多时间;问题是，如果您的UI线程已经被 ，那么它仍然有不必要的开销，向窗体的泵发送消息并处理它。
For UI-threads, however - we don't want to call Invoke lots of time; the issue is that if you are already on the UI thread, it still has the unnecessary overhead of sending a message to the form's pump and processing it.
实际上，在大多数线程代码中，你知道你希望在非 -UI线程上调用一个特定的方法，所以在这种情况下，没有额外的开销：只需调用调用。
In reality, in most threading code you know you expect a specific method to be called on a non-UI thread, so in those cases, there is no additional overhead: just call Invoke.
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