An integer value representing an index of the Single Choice Action's currently selected item.
Use this property to specify the index of Single Choice Action's item which is displayed as a selected item in a UI. Manual changing of this property value raises the SingleChoiceAction.SelectedItemChanged event. However, when an end-user changes this value by selecting an item in the Action's control, the SingleChoiceAction.Execute event is raised.
If none of the Single Choice Action's items is selected, this property returns -1.