Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        AddItem(TreeView1, TextBox1.Text)
    End Sub
 
    Private Sub AddItem(ByVal tv As TreeView, ByVal text As String)
        If tv.SelectedNode IsNot Nothing Then
            tv.SelectedNode.Nodes.Add(text)
        Else
            tv.Nodes.Add(text)
        End If
    End Sub