Implement a Tri-state CheckBox using MVVM with TreeView Some applications use checkboxes that allow an indeterminate state in addition to the two provided by a normal checkbox. This third state is shown as a dash in the checkbox, and indicates that its state is neither checked nor unchecked. This is most often used when the checkbox is tied to a collection of items in mixed states. In this video, we are going to investigate how you would do this using the RadTreeView control and the MVVM Pattern. Download the project December 5, 2013