Discuss "Console Application to change the desktop wallpaper" in the Code Samples forum.

[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;
private static readonly UInt32 SPI_GETDESKWALLPAPER = 0x73;
private static readonly int MAX_PATH = 260;
private static readonly string[] validImageFormats = new string[] { ".bmp", ".gif", ".jpg", ".jpeg", ".png", ".tif", ".tiff", ".wmf", ".emf" };

static void Main(string[] args)
{
	if (args.Length > 0)
	{
		if (args[0].Equals("-change", StringComparison.CurrentCultureIgnoreCase))
		{
			string strNewPath = (args.Length > 1) ? args[1] : String.Empty;
			if (!String.IsNullOrEmpty(strNewPath))
			{
				if (strNewPath.Equals("-random", StringComparison.CurrentCultureIgnoreCase))
				{
					strNewPath = "";
					string strFolderPath = (args.Length > 2) ? args[2] : String.Empty;
					if (!String.IsNullOrEmpty(strFolderPath))
					{
						if (Directory.Exists(strFolderPath))
						{
							strNewPath = GetRandomImage(strFolderPath);
						}
						else
						{
							ShowErrorMessage("folder does not exist: " + strFolderPath);
						}
					}
					else
					{
						ShowErrorMessage("missing folder name");
					}
				}

				if (strNewPath.Length > 0)
				{
					if (File.Exists(strNewPath))
					{
						SetWallpaper(strNewPath);
					}
					else
					{
						ShowErrorMessage("file does not exist: " + strNewPath);
					}
				}
			}
			else
			{
				ShowErrorMessage("missing file name");
			}
		}
		else if (args[0].Equals("-get", StringComparison.CurrentCultureIgnoreCase))
		{
			Console.WriteLine("current wallpaper: " + GetWallpaper());
		}
		else
		{
			ShowErrorMessage("invalid parameter: " + args[0]);
		}
	}
	else
	{
		ShowErrorMessage("not enough parameters");
	}

	Console.WriteLine(" ");
	Console.Write("press any key...");
	Console.ReadLine();
}

private static void ShowErrorMessage(string strMessage)
{
	Console.WriteLine(strMessage);
	ShowSyntax();
}

private static void ShowSyntax()
{
	string strProcessName = Process.GetCurrentProcess().ProcessName;
	Console.WriteLine(" ");
	Console.WriteLine("Available command line parameters:");
	Console.WriteLine("-get");
	Console.WriteLine("   show the disk path of current wallpaper");
	Console.WriteLine(" ");
	Console.WriteLine("-change [image path]");
	Console.WriteLine("   change the wallpaper to the image in given path");
	Console.WriteLine(" ");
	Console.WriteLine("-change -random [folder path]");
	Console.WriteLine("   change the wallpaper to random image file from the given folder");
	Console.WriteLine(" ");
	Console.WriteLine("Examples:");
	Console.WriteLine(String.Format("   {0} -get", strProcessName));
	Console.WriteLine(String.Format("   {0} -change C:\\mypictures\\coolpicture.jpg", strProcessName));
	Console.WriteLine(String.Format("   {0} -change -random C:\\mypictures", strProcessName));
}

public static void SetWallpaper(String path)
{
	try
	{
		Console.WriteLine("setting wallpaper to the file " + path + "...");
		string strBitmapPath = CopyBitmap(path);
		if (!String.IsNullOrEmpty(strBitmapPath))
		{
			SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, strBitmapPath, SPIF_UPDATEINIFILE | SPIF_SENDWININICHANGE);
			Console.WriteLine("wallpaper set successfully to " + strBitmapPath);
		}
		else
		{
			Console.WriteLine("action aborted");
		}
	}
	catch (Exception ex)
	{
		Console.WriteLine("error while setting wallpaper: " + ex.Message);
		Console.WriteLine(ex.StackTrace);
	}
}

private static string GetRandomImage(string strFolderPath)
{
	string[] arrAllImages = GetAllImages(strFolderPath);
	if (arrAllImages == null || arrAllImages.Length == 0)
	{
		Console.WriteLine("the folder '" + strFolderPath + "' does not contain valid images");
		Console.WriteLine("valid image formats: " + String.Join(", ", validImageFormats));
		return String.Empty;
	}
	int rndIndex = (new Random()).Next(0, arrAllImages.Length);
	return arrAllImages[rndIndex];
}

private static string[] GetAllImages(string strFolderPath)
{
	List<string> arrImageFiles = new List<string>();
	DirectoryInfo dirInfo = new DirectoryInfo(strFolderPath);
	foreach (FileInfo file in dirInfo.GetFiles())
	{
		if (IsImageFile(file))
		{
			arrImageFiles.Add(file.FullName);
		}
	}
	return arrImageFiles.ToArray();
}

private static bool IsImageFile(FileInfo file)
{
	string strExtension = Path.GetExtension(file.Name).ToLower();
	return (Array.IndexOf<string>(validImageFormats, strExtension) >= 0);
}

private static string CopyBitmap(string originalImagePath)
{
	Bitmap bitmap = null;
	try
	{
		bitmap = new Bitmap(originalImagePath);
	}
	catch
	{
		Console.WriteLine(originalImagePath + " is not valid bitmap!");
		return null;
	}

	string strNewImagePath = GetLocalPath(originalImagePath);
	Console.WriteLine(String.Format("trying to copy the file '{0}' to '{1}'...", originalImagePath, strNewImagePath));
	try
	{
		bitmap.Save(strNewImagePath, ImageFormat.Bmp);
		Console.WriteLine("saved successfully");
	}
	catch (Exception ex)
	{
		Console.WriteLine("error while saving: " + ex.Message);
		return null;
	}
	
	return strNewImagePath;
}

private static string GetLocalPath(string originalPath)
{
	string strRootFolderPath = Environment.GetFolderPath(Environment.SpecialFolder.MyPictures);
	string strLocalFolderPath = strRootFolderPath + Path.DirectorySeparatorChar + "DesktopBackground";
	if (!Directory.Exists(strLocalFolderPath))
	{
		Console.WriteLine("creating the directory " + strLocalFolderPath + "...");
		Directory.CreateDirectory(strLocalFolderPath);
		Console.WriteLine("created successfully");
	}
	return strLocalFolderPath + Path.DirectorySeparatorChar + Path.GetFileNameWithoutExtension(originalPath) + ".bmp";
}

private static string GetImageFormat(Bitmap bitmap)
{
	ImageFormat format = bitmap.RawFormat;
	
	if (format.Equals(ImageFormat.Bmp))
		return "bmp";
	if (format.Equals(ImageFormat.Emf))
		return "emf";
	if (format.Equals(ImageFormat.Exif))
		return "exif";
	if (format.Equals(ImageFormat.Gif))
		return "gif";
	if (format.Equals(ImageFormat.Icon))
		return "icon";
	if (format.Equals(ImageFormat.Jpeg))
		return "jpeg";
	if (format.Equals(ImageFormat.MemoryBmp))
		return "memorybmp";
	if (format.Equals(ImageFormat.Png))
		return "png";
	if (format.Equals(ImageFormat.Tiff))
		return "tiff";
	if (format.Equals(ImageFormat.Wmf))
		return "wmf";

	return null;
}

public static 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;
}