you can handle Taskbar for your application:

TaskbarHelper.SetProgressState(windowHandle, TaskbarStates.Error);

TaskbarHelper.SetProgressValue(windowHandle, 56, 100);

TaskbarHelper.FlashWindow(windowHandle);

FlashWindow

Flash Taskbar 3 times by default:

TaskbarHelper.FlashWindow(hwnd); // Or TaskbarHelper.FlashWindow(window);

Flash until Window comes to the foreground:

TaskbarHelper.FlashWindow(hwnd, TaskbarFlashFlags.FLASHW_TRAY | TaskbarFlashFlags.FLASHW_TIMERNOFG, count: 0);

Stop Flashing:

TaskbarHelper.FlashWindow(hwnd, TaskbarFlashFlags.FLASHW_STOP);

WARNING

To test it, keep in mind that clicking a button may not show the flashing effect while the app window is in the foreground. Add a delay before calling FlashWindow, for example, await Task.Delay(4000);, then minimize the app or switch to another window. This way, you can clearly see the flashing effect.

private async void ButtonClick(object sender, RoutedEventArgs e)
{
    await Task.Delay(4000);
    TaskbarHelper.FlashWindow(hwnd);
    // Now Minimize Your window immediatly
}

Demo

you can run demo and see this feature.