Why am I receiving an index out of range exception on my insertion sort?

Question

This insertion sort is for sorting the array into ascending order, when it attempt to do so I receive an index out of range exception, when this happens "j" is 0 and "i" is 1. It tries to compare the value in the first element to the value in the element with an index of "-1" which doesn't exist. What changes can I make to make this code functional?

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click

    Dim i, j, element, length As Integer
    Dim array(7) As Integer
    array(0) = 5
    array(1) = 2
    array(2) = 7
    array(3) = 6
    array(4) = 9
    array(5) = 1
    array(6) = 4
    array(7) = 8

    length = array.Length


    For i = 1 To length - 1
        j = i
        While j > 0 And array(j) < array(j - 1)
            If array(j - 1) > array(j) Then
                element = array(j)
                array(j) = array(j - 1)
                j = j - 1
                array(j) = element
            End If
        End While
    Next



    For Index As Integer = 0 To 7
        ListBox1.Items.Add(array(Index))
    Next


End Sub

Answer 1

Your line saying

While j > 0 And array(j) < array(j - 1)

will give an index out of range error whenever j is zero (because j - 1 will be -1 and you don't have a array(-1) element).

Change that line to

While j > 0 AndAlso array(j) < array(j - 1)

so that the second part of the test is only evaluated if the first part is True.