点击回应、关闭确认以及另一种获取设备环境句柄的方法

switch (message)
	{
	……
	case WM_LBUTTONUP://当鼠标左键弹起
		MessageBox(NULL, TEXT("I was clicked"), TEXT("Client"), MB_OK);
		return 0;
        ……
	}

switch (message)
	{
	……
	case WM_CLOSE://点击关闭按键时
		if (MessageBox(hwnd, TEXT("Really want to quit?"), TEXT("Request confirming"), MB_YESNO) == IDYES)
			DestroyWindow(hwnd);
		else
			return 0;
	……
	}

	hdc = GetDC(hwnd);
        //这里放置代码，此方法不需要响应WM_PAINT
	ReleaseDC(hwnd, hdc);