C# Definition:

[StructLayout(LayoutKind.Sequential)]
public struct WALLPAPEROPT
{
     public static readonly int SizeOf = Marshal.SizeOf(typeof(WALLPAPEROPT));
     public int dwSize;
     public WallPaperStyle dwStyle;
}

VB Definition:

<StructLayout(LayoutKind.Sequential)> _
Public Structure WALLPAPEROPT
    Public Shared ReadOnly SizeOf As Integer
    Public dwSize As Integer
    Public dwStyle As WallPaperStyle
    Shared Sub New()
    WALLPAPEROPT.SizeOf = Marshal.SizeOf(GetType(WALLPAPEROPT))
    End Sub
End Structure

User-Defined Field Types:

None.

Notes:

WALLPAPEROPT opts = new WALLPAPEROPT();
opts.dwSize = WALLPAPEROPT.SizeOf;

See WallPaperStyle.