TreeViewItem.OverlayImageIndex Property

A numeric value that represents the index of the tree view item's overlay image in the image list. Overlay images are images that are drawn over the item's main image. A tree view can have up to four overlay images, so this value can be in the range of 1 to 4.

 VIRTUAL PROPERTY OverlayImageIndex AS USUAL GET SET 

public virtual Usual OverlayImageIndex { get; set; }