Powershell script from shortcut to change desktop

Question

Any ideas and suggestions on why this works when run from w/in PS, but not when run from a shortcut defined as:

%SystemRoot%\system32\WindowsPowerShell\v1.0\powershell.exe -File "C:\Users\bin\ChangeDesktop.ps1"

Contents of ChangeDesktop.ps1:

set-itemproperty -path "HKCU:Control Panel\Desktop" -name WallPaper -value ""
rundll32.exe user32.dll, UpdatePerUserSystemParameters

If I am in the PS "command prompt" environment the desktop background is automatically removed and refreshed, outside of that I have to manually refresh the desktop to effect the change.

System is Windows Server 2008 R2 - fresh install. Script executionpolicy is set to RemoteSigned, and I don't see any PS errors. I Just don't see the desktop refresh automatically when running from a desktop shortcut.

scratches head

Answer 1

rundll32.exe user32.dll, UpdatePerUserSystemParameters didn't actually change the wallpaper for me on a 2008 x64 box. This does did though... It calls the Win32 API to invoke changing the wallpaper. If you save this as your ChangeDesktop.ps1 script it should work. As it is below it will remove any desktop wallpaper. However if you do want to set one you can edit the last line with the path of a supported image file like this:

[Wallpaper.Setter]::SetWallpaper( 'C:\Wallpaper.bmp', 0 )

The second argument is for the styling:

0: Tile 1: Center 2: Stretch 3: No Change

The script:

Add-Type @"
using System;
using System.Runtime.InteropServices;
using Microsoft.Win32;
namespace Wallpaper
{
   public enum Style : int
   {
       Tile, Center, Stretch, NoChange
   }
   public class Setter {
      public const int SetDesktopWallpaper = 20;
      public const int UpdateIniFile = 0x01;
      public const int SendWinIniChange = 0x02;
      [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
      private static extern int SystemParametersInfo (int uAction, int uParam, string lpvParam, int fuWinIni);
      public static void SetWallpaper ( string path, Wallpaper.Style style ) {
         SystemParametersInfo( SetDesktopWallpaper, 0, path, UpdateIniFile | SendWinIniChange );
         RegistryKey key = Registry.CurrentUser.OpenSubKey("Control Panel\\Desktop", true);
         switch( style )
         {
            case Style.Stretch :
               key.SetValue(@"WallpaperStyle", "2") ; 
               key.SetValue(@"TileWallpaper", "0") ;
               break;
            case Style.Center :
               key.SetValue(@"WallpaperStyle", "1") ; 
               key.SetValue(@"TileWallpaper", "0") ; 
               break;
            case Style.Tile :
               key.SetValue(@"WallpaperStyle", "1") ; 
               key.SetValue(@"TileWallpaper", "1") ;
               break;
            case Style.NoChange :
               break;
         }
         key.Close();
      }
   }
}
"@

[Wallpaper.Setter]::SetWallpaper( '', 0 )

Originally from PoshCode: http://poshcode.org/491