Changing the Desktop Wallpaper with C#

These code snippets will show you how to:

• Set the current wallpaper.
• Get the path of the current wallpaper.
• Detect when the current wallpaper changes.

How to set the desktop wallpaper:

using System.Runtime.InteropServices;

[DllImport("user32.dll", CharSet = CharSet.Auto)]
private static extern Int32 SystemParametersInfo(
    UInt32 action, UInt32 uParam, String vParam, UInt32 winIni);

private static readonly UInt32 SPI_SETDESKWALLPAPER  = 0x14;
private static readonly UInt32 SPIF_UPDATEINIFILE    = 0x01;
private static readonly UInt32 SPIF_SENDWININICHANGE = 0x02;

public void SetWallpaper(String path)
{
    SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, path,
        SPIF_UPDATEINIFILE | SPIF_SENDWININICHANGE);
}

How to get the path of the current desktop wallpaper:

using System.Runtime.InteropServices;

[DllImport("user32.dll", CharSet = CharSet.Auto)]
private static extern Int32 SystemParametersInfo(
    UInt32 action, UInt32 uParam, IntPtr vParam, UInt32 winIni);

private static readonly UInt32 SPI_GETDESKWALLPAPER = 0x73;
private static readonly int    MAX_PATH             = 260;

public String GetWallpaper()
{
    String wallpaper = new String('\ 0', MAX_PATH);
    SystemParametersInfo(SPI_GETDESKWALLPAPER,
        (UInt32)wallpaper.Length, wallpaper, 0);
    wallpaper = wallpaper.Substring(0, wallpaper.IndexOf('\ 0'));
    return wallpaper;
}

How to detect when the desktop wallpaper changes:

using System.Windows.Forms;

public class MyApp : Form
{
    private static readonly UInt32 SPI_SETDESKWALLPAPER = 0x14;
    private static readonly UInt32 WM_SETTINGCHANGE     = 0x1A;

    protected override void WndProc(ref Message message)
    {
        if (message.Msg == WM_SETTINGCHANGE)
        {
            if (message.WParam.ToInt32() == SPI_SETDESKWALLPAPER)
            {
                // Handle that wallpaper has been changed.
            }
        }

        base.WndProc(ref message);
    }
}

Of course, you should add return value checking and exception handling where appropriate.

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Tags: .NET, C#, Desktop Wallpaper