试图删除具有相同索引的两个ListBox但是这与其他代码冲突？

Question

我有两个列表框，成分和数量。我想单击一个列表框，当按下删除时，这将删除这些列表框的索引中的项目，但它总是抱怨索引为-1。这是代码：

    Private Sub Ingredients_SelectedIndexChanged(sender As Object, e As EventArgs) Handles Ingredients.SelectedIndexChanged
    'Dim IndexVal As Integer = Ingredients.SelectedIndex
    'Dim TextInIndexOfIngredients As String = Ingredients.Items(IndexVal).ToString()
    'Dim TextInIndexOfQuantity As String = Quantity.Items(IndexVal).ToString()
    'MsgBox("Recipe:" + TextInIndexOfIngredients + " Quantity:" + TextInIndexOfQuantity)
End Sub

Private Sub Form1_KeyDown(ByVal sender As Object, _
ByVal e As System.Windows.Forms.KeyEventArgs) Handles Ingredients.KeyDown
    If e.KeyCode = Keys.Delete Then
        If Ingredients.SelectedIndex = 0 Then
            Ingredients.Items.Clear()
        Else
            Dim index As Integer = Ingredients.SelectedIndex
            Ingredients.Items.RemoveAt(index)
            Quantity.Items.RemoveAt(index)
        End If


    End If
End Sub

不知道如何解决这个问题，尝试了一切。清除工作正常。