internal static void Remove(DynamicDataGrid grid, object model)
        {
            var i = GetItems(grid);

            i.Remove(model);
            grid.OnPropertyChanged("SelectedItems");
        }
        internal static void SetChecked(DynamicDataGrid grid, object model, bool state)
        {
            var i = GetItems(grid);

            if (!i.ContainsKey(model))
            {
                i.Add(model, false);
            }

            i[model] = state;
            grid.OnPropertyChanged("SelectedItems");
        }