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   | LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {     HMENU hmenu, haddmenu;     switch(message)     {     case WM_COMMAND :         switch (LOWORD(wParam))         {         case 1 :              hmenu = GetMenu(hWnd);             haddmenu = CreateMenu();             AppendMenu(haddmenu, MF_ENABLED, 4, "求和");             AppendMenu(haddmenu, MF_ENABLED, 5, "求差");             InsertMenu(hmenu, 2, MF_POPUP | MF_BYPOSITION, (UINT)haddmenu, "统计计算");             EnableMenuItem(hmenu, 1, MF_GRAYED);             EnableMenuItem(hmenu, 2, MF_ENABLED);             DrawMenuBar(hWnd);             break;         case 2 :              hmenu = GetMenu(hWnd);             DeleteMenu(hmenu, 2, MF_BYPOSITION);             EnableMenuItem(hmenu, 1, MF_ENABLED);             EnableMenuItem(hmenu, 2, MF_GRAYED);             DrawMenuBar(hWnd);             break;         }         break;     } }
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