Silverlight DataGrid CellEditTemplate combobox databinding issue.

I am working on a SilverLight app on ASPX with RIA services from Entity Framework backend. I have the loading of the DataGrid just fine including the related table data. I am now working on updating the fields with the combobox changes. As I debug I can see the changes on the entity object, but it does not persist. I tried calling CommitEdit on the DataGrid in the RowEditEnding event which just crashes the app with giving me the error.

Bind the CB's:

Private Sub dgStaff_PreparingCellForEdit(sender As Object, e As System.Windows.Controls.DataGridPreparingCellForEditEventArgs) Handles dgStaff.PreparingCellForEdit
   columnIndex = e.Column.DisplayIndex
   Dim cb As ComboBox = TryCast(e.EditingElement, ComboBox)
   If cb IsNot Nothing Then
     cb.DisplayMemberPath = "Description"
     Select Case columnIndex
       Case 2
         cb.SelectedItem = curPerson.Station.StationId
         cb.ItemsSource = stations
         cb.SelectedValue = curPerson.Station.StationId
       Case 3
         cb.SelectedItem = curPerson.Shift.ShiftId
         cb.ItemsSource = shifts
         cb.SelectedValue = curPerson.Shift.ShiftId
       Case 4
         cb.SelectedItem = curPerson.Team.TeamId
         cb.ItemsSource = teams
         cb.SelectedValue = curPerson.Team.TeamId
     End Select
   End If
End Sub

Get the current entity object:

Private Sub dgStaff_BeginningEdit(sender As Object, e As System.Windows.Controls.DataGridBeginningEditEventArgs) Handles dgStaff.BeginningEdit
    curPerson = CType(e.Row.DataContext, BMServiceRef.Personnel)
End Sub

Get the new values and apply them to the entity object:

Private Sub cb_SelectionChanged(sender As System.Object, e As System.Windows.Controls.SelectionChangedEventArgs)
  Dim cb As ComboBox = DirectCast(sender, ComboBox)
  Select Case columnIndex
    Case 2
      curPerson.StationId = CType(cb.SelectedItem, BMServiceRef.Station).StationId
    Case 3
      curPerson.ShiftId = CType(cb.SelectedItem, BMServiceRef.Shift).ShiftId
    Case 4
      curPerson.TeamId = CType(cb.SelectedItem, BMServiceRef.Team).TeamId
  End Select
End Sub

Let me know if I can add any more info. Thanks for looking...

Tags: Silverlight