The insert method overwrites the index and adds extraneous value at the end of the ArrayList.

[FullValueRider]

The ArrayList drop in replacement Insert method is in error as it is overwriting the item at the index rather than inserting, and adding an extraneous value at the end of the ArrayList.

Sub TestArrayListItem()
        Dim myAL As ArrayList = ArrayList(Array(10, 20, 30, 40, 50, 60, 70))
        Fmt.Dbg "{0}", myAL
        myAL.Item(3) = 42
        Fmt.Dbg "{0}", myAL
        myAL.Insert 3, 84
        Fmt.Dbg "{0}", myAL
        myAL.Insert 5, 84
        Fmt.Dbg "{0}", myAL
        
    End Sub

gives the folowing output

{10,20,30,40,50,60,70}
{10,20,30,42,50,60,70}
{10,20,30,84,50,60,70,Empty}
{10,20,30,84,50,84,70,0,Empty}