changing background

Imports System.Runtime.InteropServices
Module Module1
Private Declare Auto Function SystemParametersInfo Lib "user32.dll" (ByVal uAction As Integer, ByVal uParam As Integer, ByVal szImagePath As String, ByVal fuWinIni As Integer) As Boolean
Private Const SPI_SETDESKWALLPAPER As Integer = &H14
Private Const SPIF_UPDATEINIFILE As Integer = &H1
Private Const SPIF_SENDCHANGE As Integer = &H2

Public Function ChangeWallpaper(ByVal path As String) As Boolean
Return SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, path, SPIF_UPDATEINIFILE Or SPIF_SENDCHANGE)
End Function
End Module

Windows doesn't like to deal with .jpeg files, just .bmp files.

The shell can, it offers the IActiveDesktop::SetWallpaper()

method. Unfortunately, the COM component that implements this

method (shell32.dll) doesn't export the IActiveDesktop interface so you

don't have a declaration available for it to use in your program.

That is what makes dealing with the shell so difficult in .NET, we need

a Primary Interop Assembly for the shell but none is available

(AFAIK). I hope MSFT is paying attention here.

A workaround for you is to convert the .jpeg file to a .bmp file yourself. Here's code to do this:

Imports System.Runtime.InteropServices

Imports System.Drawing

Module Module1

Private Declare Auto Function SystemParametersInfo Lib

"user32.dll" (ByVal uAction As Integer, ByVal uParam As Integer, ByVal

szImagePath As String, ByVal fuWinIni As Integer) As Boolean

Private Const SPI_SETDESKWALLPAPER As Integer = &H14

Private Const SPIF_UPDATEINIFILE As Integer = &H1

Private Const SPIF_SENDCHANGE As Integer = &H2

Public Function ChangeWallpaper(ByVal path As String) As Boolean

path = ConvertBitmap(path)

Return SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, path, SPIF_UPDATEINIFILE Or SPIF_SENDCHANGE)

End Function

Private Function ConvertBitmap(ByVal srce As String) As String

' Convert image file <srce> to a bitmap file, stored in My Pictures

Dim sbmp As New Bitmap(srce)

Dim dbmp As New Bitmap(sbmp.Width, sbmp.Height, Imaging.PixelFormat.Format24bppRgb)

Dim gr As Graphics = Graphics.FromImage(dbmp)

gr.DrawImage(sbmp, 0, 0)

Dim path As String = System.Environment.GetFolderPath(Environment.SpecialFolder.MyPictures)

path += "\wallpaper.bmp"

dbmp.Save(path, Imaging.ImageFormat.Bmp)

sbmp.Dispose()

dbmp.Dispose()

Return path

End Function