SendMessage(HWND, BM_CLICK, 0, 0);点击成功和失败的返回值分别是什么？
有一种东西叫MSDN。Return value
This message does not return a value
（此消息不返回一个值）https://msdn.microsoft.com/en-us/library/windows/desktop/bb775985(v=vs.85).aspx
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