C#

ViolationsUniquePenaltyApplied = (from a in violations
                                  join b in programs on a.ViolationTypeId equals b.ViolationTypeId
                                  join d in branches on b.BranchId equals d.BranchId
                                  join e in programs on a.ViolationSubtypeId equals e.ViolationTypeId into es from e in es.DefaultIfEmpty()
                                  where a.ApplyUniquePenalty == true
                                  group new { a.ViolationSubtypeId, e.ViolationTypeName, a?.ViolationTypeId, b?.ViolationTypeName, b?.ParentViolationId, d?.BranchId, d?.Name, a.PenaltyAssessed, a.ViolationId, a.ViolationNumber }
                                  by new { a?.ViolationTypeId, b?.ViolationTypeName, d?.BranchId, d?.Name, a.ViolationId }
                    into g
                                  select new
                                  {
                                      ViolationTypeId = g.FirstOrDefault().ViolationTypeId,
                                      ViolationType = g.FirstOrDefault().ViolationTypeName,
                                      ParentViolationType = (g.FirstOrDefault()?.ParentViolationId != null) ? (from e in programs where g.FirstOrDefault()?.ViolationTypeId == e.ParentViolationId select e.ViolationTypeName)?.FirstOrDefault() : g.FirstOrDefault().ViolationTypeName,
                                      BranchId = g.FirstOrDefault().BranchId,
                                      Branch = g.FirstOrDefault().Name,
                                      PenaltyAssessed = g.Sum(pc => pc.PenaltyAssessed),
                                      Cnt = g.Count(),
                                      ViolationNumber = g.FirstOrDefault().ViolationNumber,
                                      CountOrId = (g.Count() == 1) ? g.Count() : g.FirstOrDefault().ViolationId,
                                      PenaltyPerUnit = g.Sum(pc => pc.PenaltyAssessed) / g.Count()
                                  })

public Form1()
       {
           ExcelDataSource myExcelSource = new ExcelDataSource();
           myExcelSource.FileName = @"C:\Users\Fardin\Desktop\Book1.xlsx";
           ExcelWorksheetSettings worksheetSettings = new ExcelWorksheetSettings("Sheet1", "A1:B20");
           myExcelSource.SourceOptions = new ExcelSourceOptions(worksheetSettings);
           myExcelSource.SourceOptions.SkipEmptyRows = false;
           myExcelSource.SourceOptions.UseFirstRowAsHeader = true;
           myExcelSource.Fill();
           pivotGridControl1.DataSource = myExcelSource;
       }

System.NullReferenceException: 'Object reference not set to an instance of an object.'