.NET Framework 4.6 and 4.5
When overridden in a derived class, gets or sets the zero-based index of the currently selected item.
abstract SelectedIndex : int with get, set
Type: System.Int32A zero-based index of the currently selected item. A value of negative one (-1) is returned if no item is selected.
Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1
.NET Framework Client Profile
Supported in: 4, 3.5 SP1