Box. Selected Index Collection. Index Of(Int32) Method
public: int IndexOf(int selectedIndex);
public int IndexOf (int selectedIndex);
member this.IndexOf : int -> int
Public Function IndexOf (selectedIndex As Integer) As Integer
The zero-based index from the ListBox.ObjectCollection to locate in this collection.
Once you know that an item is located within the collection (using the Contains method), you can use the IndexOf method to determine where a specific index position within the ListBox.ObjectCollection for the ListBox is stored within the ListBox.SelectedIndexCollection.