Textbox lines to listbox? "Index was outside the bounds of the arr

Hi, I'm making a program and a small part of it includes a multi-line textbox and a listbox.
After entering text into the textbox the user would click a button and each line in the textbox will become an item in the listbox.

Here's the code I have:

Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Dim ii As Integer
        Dim a As String = ""
        ii = TextBox1.Lines.Count()
        ListBox1.Items.Clear()
        For i As Integer = 1 To ii
            a = TextBox1.Lines(i)
            ListBox1.Items.Add(a)
        Next i
End Sub

When I run it I get the following error "Index was outside the bounds of the array."

I'd very much apritiate it if someone could help me