wpf, vb.net, vs2013, DataGrid with Combo Box.

Hello

I have a data grid (DG). I want to add a combo box to the data grid(dg). The combo box should immediately be visible in the data grid. So I want to have that with a click the combo box is opened.

So far what I have done.

Dim dtCountry As New DataTable
Dim sQry As String

sQry = "Select COUNTRY_ID, COUNTRY_NAME from ST_country where rec_deleted = 0"
dtCountry = cMain.GetDataTable(sQry)

Dim col As New DataGridTemplateColumn()
Dim fac As New FrameworkElementFactory(GetType(ComboBox))

fac.SetValue(ComboBox.ItemsSourceProperty, dtCountry.DefaultView)
fac.SetValue(ComboBox.DisplayMemberPathProperty, "COUNTRY_NAME")

fac.SetBinding(ComboBox.SelectedValuePathProperty, New Binding("COUNTRY_NAME"))

Dim celli As New DataTemplate()
With celli
    .VisualTree = fac
End With

With col
   .Header = "Country"
   .CellEditingTemplate = celli
   .CellTemplate = celli
   .SortMemberPath = "COUNTRY_NAME"
End With

DG.Columns.Add(col)

If I selected a country de datagrid wil not be update. And if I start the program I see a datagrid with empty combo  boxen.

Please can someone help me.