Сортировка названий месяцев в ListBox

Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim Mnths As New List(Of Mnth)
        For Each M As String In ListBox1.Items
            Dim monthNumber = DateTime.ParseExact(M, "MMMM", Globalization.CultureInfo.CurrentCulture).Month
            Mnths.Add(New Mnth With {.Month = M, .Number = monthNumber})
        Next
        Mnths.Sort(Function(a As Mnth, b As Mnth) a.Number.CompareTo(b.Number))
        ListBox1.Items.Clear()
        ListBox1.Items.AddRange(Mnths.ToArray)
    End Sub
    Class Mnth 'Наш класс
        Public Month As String
        Public Number As Integer
        Public Overrides Function ToString() As String
            Return Month
        End Function
    End Class
End Class

ListBox1.Items.AddRange(Mnths.ToArray)

ListBox1.Items.AddRange(Mnths.ToString.ToArray)

ListBox1.Items.AddRange(Mnths.ToArray.ToString)

ToString

Private Sub addbtn_Click(sender As Object, e As EventArgs) Handles addbtn.Click
        Dim Mnths As New List(Of Mnth)
        For Each M As String In ListBox1.SelectedItems
            Dim monthNumber = DateTime.ParseExact(M, "MMMM", Globalization.CultureInfo.InvariantCulture).Month
            Mnths.Add(New Mnth With {.Month = M, .Number = monthNumber})
        Next
        Mnths.Sort(Function(a As Mnth, b As Mnth) a.Number.CompareTo(b.Number))
        'ListBox2.Items.Clear()
        ListBox2.Items.AddRange(Mnths.ToArray)
    End Sub