For a standard System.Windows.Forms.ListBox, you can use this property to determine the index of the item that is selected in the System.Windows.Forms.ListBox. If the ListBox.SelectionMode property of the System.Windows.Forms.ListBox is set to either SelectionMode.MultiSimple or SelectionMode.MultiExtended (which indicates a multiple-selection System.Windows.Forms.ListBox) and multiple items are selected in the list, this property can return the index to any selected item.

To retrieve a collection containing the indexes of all selected items in a multiple-selection System.Windows.Forms.ListBox, use the ListBox.SelectedIndices property. If you want to obtain the item that is currently selected in the System.Windows.Forms.ListBox, use the ListBox.SelectedItem property. In addition, you can use the ListBox.SelectedItems property to obtain all the selected items in a multiple-selection System.Windows.Forms.ListBox.