When manually defining foreign key descriptions because the AutoCreateForeignKeyDescriptions property is set to false, the ItemsSource property and the ValuePath properties must be set in order to specify the source from which the values will be retrieved as well as their path, which represents the primary key of the foreign item in the ItemsSource.
Requirements
Target Platforms: Windows 11, Windows 10, 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