SendMessage VS PostMessage

/// <param name="hwnd">handle of destination window</param>
/// <param name="wMsg">message to post</param>
/// <param name="wParam">first message parameter</param>
/// <param name="lParam">second message parameter</param>
const string Dowm = 0x100;
const string Up = 0x101
[DllImport("user32.dll", EntryPoint = "SendMessageA")]
static extern int SendMessage(IntPtr hwnd, int wMsg, IntPtr wParam, IntPtr lParam);
[DllImport("User32.dll")]
static extern bool PostMessage(IntPtr hwnd, int wMsg, IntPtr wParam, IntPtr lParam);

SendMessage用在你需要馬上知道這個Message處理的結果
PostMessage只是把訊息丟入Message Queue會在下次進入訊息迴圈時才處理