public IActionResult ExportDataSheet(string filter)
        {
            var expression = _dataSheetHelper.SearchForExcel(filter);

            if (expression == null)
            {
                expression = PredicateBuilder.True <DataSheet>();
            }
            expression = expression.And(k => k.FTSUser == null);

            List <DataSheetWaitingForAdminDto> dataSheetDtos = _dataSheetService.GetDataSheetWaitingForAdminDtos(expression);

            string[] columns = { "Müşteri Adı", "Kayıt No", "Kayıt Yapan", "Kayıt Tarihi", "Departman", "Ana Müşteri", "Ana Müşteri Model No",
                                 "Model No",    "Durum" };
            byte[]   filecontent = ExcelExportHelper.ExportExcel(dataSheetDtos, "FTSDataSheet", true, columns);
            return(File(filecontent, ExcelExportHelper.ExcelContentType, "FTSDataSheet.xlsx"));
        }