How to force Windows desktop background to update or refresh

RUNDLL32.EXE USER32.DLL,UpdatePerUserSystemParameters 1, True

• Open Task manager
• Kill explorer.exe
• If the shell doesn't immediately restart
• From the menu select File > New Task
• Type "explorer.exe" and hit enter.

Change the screen resolution, then choose the revert option. Your resolution will remain the same and the background will have changed.

Alternatively, disconnect and reconnect the display cable.

I was trying to do something similar - update a registry setting for the start menu and then immediately have the start menu reflect the changes.

The solution from this MSDN question worked for me perfectly.

You could try broadcasting a WM_SETTINGCHANGE message. For example:

class Program
{
    [DllImport("user32.dll", SetLastError = true)]
    private static extern IntPtr SendMessageTimeout(IntPtr hWnd, int Msg, IntPtr wParam, string lParam, uint fuFlags, uint uTimeout, IntPtr lpdwResult);

    private static readonly IntPtr HWND_BROADCAST = new IntPtr(0xffff);
    private const int WM_SETTINGCHANGE = 0x1a;
    private const int SMTO_ABORTIFHUNG = 0x0002;

    static void Main(string[] args)
    {
        SendMessageTimeout(HWND_BROADCAST, WM_SETTINGCHANGE, IntPtr.Zero, null, SMTO_ABORTIFHUNG, 100, IntPtr.Zero);
    }
}