I have a class that inherits ObservableCollection.  Initially the collection is empty. When I bind it to the data grid and set the allow new to true.  The add new row does not show up.

Here is some code:

  this.xamDataGridTasks.DataSource=_contract.Tasks;
            this.xamDataGridTasks.FieldLayoutSettings.AllowAddNew = true;
            this.xamDataGridTasks.FieldLayoutSettings.AddNewRecordLocation = Infragistics.Windows.DataPresenter.AddNewRecordLocation.OnTop;