The format of the filter is a comma delimited list of file types (ex "*.gif,*.jpg,*.bmp"). The filter is also used by the HtmlBoxUpload.FileTypeMustMatchFilter property, which controls whether or not file types that do not match the filter are uploaded.
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