Items whose CheckState property returns 'Indeterminate' are not included in the CheckedItems collection.
The CheckedItems property is similar to the property of the same name exposed by the .NET CheckedListBox control.
When the EditorWithCombo's EditorValueSource property is set to 'CheckedItems', the editor's value consists of a list containing the DataValue of each checked item; the CheckedItems collection returns a list of the same size, but which includes references to those items as opposed to their values.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, 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