Extracting Each Line Of RichTextBox And Numbering It

I have two RichTextBox's; rtb1 and rtb2. I want to convert the contents of rtb1 to rtb2, but add a number at the start of each line.

So from:
[v]hello[/v]
[v]goodbye[/v]

To:
1. [v]hello[/v]
2. [v]goodbye[/v]

VB.NET
Private Sub btnProduce_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnProduce.Click
Dim List As String = rtb1.Text
If (chkPrefix.Checked = True) Then
List = Replace(List, "[v]", ". [v]")
End If
'Display new list
rtb2.Text = List
End Sub