AlphaLevel ranges from 0 (completely transparent) to 255 (opaque).
When the AlphaLevel has been set to completely transparent, the Legend box will not be filled unless it is a scale (which renders in the spectral scales own colors), however any icons and text are rendered as if appearing in mid-air.
The effect of specifying an AlphaLevel with this property, and a separate alpha-component on BackgroundColor, is undefined.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2