Gets or sets the index of a tab (tabbed page) which is selected within the TabControl.
A tabbed extension (which can be either the TabControl or PageControl) allows end users to select tabs via mouse clicks. In order to make a particular tab (tabbed page) active via code use the ActiveTabIndex property. This property specifies the active tab's index within the TabControlSettings.Tabs (PageControlSettings.TabPages) collection of a tabbed extension.
A tabbed extension always has an active tab and only one tab can be active within the extension at a time.