columns.AddColumn(column =>
              {
                  column.PropertyName<WorkBookGridModel>(x => x.FinalMark);
                  column.CellsHorizontalAlignment(HorizontalAlignment.Center);
                  column.IsVisible(true);
                  column.Order(2);
                  column.HeaderCell("نمره");
                    column.AggregateFunction(aggregateFunction =>
                    {
                        aggregateFunction.NumericAggregateFunction(AggregateFunction.Average);
                    });

              });
          })
               .MainTableSummarySettings(summary =>
               {
                   summary.OverallSummarySettings("Summary");
               })