1 `Disconnected Mode`

//GetChanges return added rows before update datasource from caching
var newRows = YourDataTable.GetChanges(DataRowState.Added);

DataColumn columnFlag = new DataColumn("FlagDelete", typeof(bool));

2 `Connected Mode`

<DataGridTemplateColumn>
   <DataGridTemplateColumn.CellTemplate>
      <DataTemplate>
          <Button Content="Remove" Command="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type TabControl}}, Path=DataContext.BottomDetailVM.DeleteCommand}" Visibility="{Binding IsNew, Converter={StaticResource Bool2VisibilityConverter}, FallbackValue=Collapsed}" CommandParameter="{Binding}" />
      </DataTemplate>
   </DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>

public ICommand DeleteRangfolgeCommand
{
  get
  {
     return new ActionCommand<MyOwnViewModel>(ExecuteDelete);
  }
}

private void ExecuteDelete(MyOwnViewModel viewModelToDelete)
{
    this.ItemsSourceList.Remove(viewModelToDelete);
}