Datagrid sorting doesn't work

Hello,

I have a Datagrid. The data of the datagrid is from an object array. I can't select the columns to sort the data. What is wrong?
The data is shown in the datagrid correctly.

VB Code:

Dim subtypeTableStylelagerbestaende As New DataGridTableStyle
        subtypeTableStylelagerbestaende.AlternatingBackColor() = Color.LightYellow
        subtypeTableStylelagerbestaende.BackColor() = Color.White
        subtypeTableStylelagerbestaende.AllowSorting() = True
        Dim colSubTypelagerbestaende1 As New DataGridTextBoxColumn
        With colSubTypelagerbestaende1
            .HeaderText = ""
            .MappingName = "ID"
            .Width = 0
        End With
        Dim colSubTypelagerbestaende2 As New DataGridTextBoxColumn
        With colSubTypelagerbestaende2
            .HeaderText = ""
            .MappingName = "produktID"
            .Width = 0
        End With
        Dim colSubTypelagerbestaende3 As New DataGridTextBoxColumn
        With colSubTypelagerbestaende3
            .HeaderText = "Lager"
            .MappingName = "lager"
            .NullText = ""
            .Width = 75
        End With
        Dim colSubTypelagerbestaende4 As New DataGridTextBoxColumn
        With colSubTypelagerbestaende4
            .HeaderText = "A-Nummer"
            .MappingName = "artikelnummer"
            .NullText = ""
            .Width = 60
        End With
        Dim colSubTypelagerbestaende5 As New DataGridTextBoxColumn
        With colSubTypelagerbestaende5
            .HeaderText = "Land"
            .MappingName = "eigenschaft1"
            .NullText = ""
            .Width = 140
        End With
        Dim colSubTypelagerbestaende6 As New DataGridTextBoxColumn
        With colSubTypelagerbestaende6
            .HeaderText = "Nominalwert"
            .MappingName = "eigenschaft2"
            .NullText = ""
            .Width = 80
            .Alignment = HorizontalAlignment.Right
        End With
        Dim colSubTypelagerbestaende7 As New DataGridTextBoxColumn
        With colSubTypelagerbestaende7
            .HeaderText = "Jahrgang"
            .MappingName = "eigenschaft3"
            .NullText = ""
            .Width = 80
            .Alignment = HorizontalAlignment.Center
        End With
        Dim colSubTypelagerbestaende8 As New DataGridTextBoxColumn
        With colSubTypelagerbestaende8
            .HeaderText = "Bestand"
            .MappingName = "bestand"
            .NullText = 0
            .Width = 80
            .Alignment = HorizontalAlignment.Right
        End With
 
        subtypeTableStylelagerbestaende.GridColumnStyles.Add(colSubTypelagerbestaende1)
        subtypeTableStylelagerbestaende.GridColumnStyles.Add(colSubTypelagerbestaende2)
        subtypeTableStylelagerbestaende.GridColumnStyles.Add(colSubTypelagerbestaende3)
        subtypeTableStylelagerbestaende.GridColumnStyles.Add(colSubTypelagerbestaende4)
        subtypeTableStylelagerbestaende.GridColumnStyles.Add(colSubTypelagerbestaende5)
        subtypeTableStylelagerbestaende.GridColumnStyles.Add(colSubTypelagerbestaende6)
        subtypeTableStylelagerbestaende.GridColumnStyles.Add(colSubTypelagerbestaende7)
        subtypeTableStylelagerbestaende.GridColumnStyles.Add(colSubTypelagerbestaende8)
        subtypeTableStylelagerbestaende.MappingName = "clager[]"
        DataGrid_lagerbestaende_Form1.TableStyles.Add(subtypeTableStylelagerbestaende)
        DataGrid_lagerbestaende_Form1.AllowSorting() = True
...
...
...
Dim mylager() As clager
...
DataGrid_lagerbestaende_Form1.DataSource = mylager