public ActionResult Index()
{
            NewsContext db = new NewsContext();
            var Query = db.Employee.ToList()
            return View(Query);
}

که با تغییر کد به شکل زیر حل شد 

public ActionResult Index(){
            NewsContext db = new NewsContext();
            var Query = db.Employee.ToList().Where(x=>x.ManagerID==null).ToList();
            return View(Query);
}

if (args.CellType == CellType.PreviousPageSummaryCell ||
                      args.CellType == CellType.PageSummaryCell ||
                      args.CellType == CellType.SummaryRowCell)
                    {
                        if (args.TableRowData != null)
                        {
                            var summaryRowRemain = args.TableRowData.FirstOrDefault(x => x.PropertyName == "CaclulatedRemains");
                            if (summaryRowRemain != null && args.Cell.RowData.PropertyName == "CaclulatedDetection")
                            {
                                args.Cell.RowData.FormattedValue = (summaryRowRemain.PropertyValue.ToSafeDouble() > 0)
                                    ? "بستانکار"
                                    : (summaryRowRemain.PropertyValue.ToSafeDouble() < 0 ? "بدهکار" : string.Empty);
                            }
                        }
                    }

columns.AddColumn(column =>
                {
                    column.PropertyName<VoucherRowPrintViewModel>(x => x.CaclulatedDetection);
                    column.CellsHorizontalAlignment(PdfRpt.Core.Contracts.HorizontalAlignment.Left);
                    column.IsVisible(true);
                    column.Order(4);
                    column.Width(1);
                    column.AggregateFunction(aggregateFunction =>
                    {
                        aggregateFunction.NumericAggregateFunction(AggregateFunction.Empty);
                    });
                    column.HeaderCell("تشخیص");
                });
                columns.AddColumn(column =>
                {
                    column.PropertyName<VoucherRowPrintViewModel>(x => x.CaclulatedRemains);
                    column.CellsHorizontalAlignment(PdfRpt.Core.Contracts.HorizontalAlignment.Right);
                    column.IsVisible(true);
                    column.Order(5);
                    column.Width(2);
                    column.ColumnItemsTemplate(template =>
                    {
                        template.TextBlock();
                        template.DisplayFormatFormula(obj => obj == null ? string.Empty : string.Format("{0:n0}", (Math.Abs(Convert.ToInt64(obj.ToSafeString().Replace(",", string.Empty))))));
                    });
                    column.AggregateFunction(aggregateFunction =>
                    {
                        aggregateFunction.NumericAggregateFunction(AggregateFunction.Sum);
                        aggregateFunction.DisplayFormatFormula(obj => obj == null ? string.Empty : string.Format("{0:n0}", (Math.Abs(Convert.ToInt64(obj.ToSafeString().Replace(",", string.Empty))))));
                    });
                    column.HeaderCell("مانده");
                });