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.

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);
    }
}