"Object reference not set to an instance of an object" LINQ join error

Question

Hi All,

I am joining the tables using LINQ. I am getting the error while running "Object reference not set to an instance of an object" . Don't know where I am missing.

 

var leadlist = from lead in _context.CallDetail.Include(z => z.OutCome).Where(x => x.IsDeleted != true).ToList()       join appoint in _context.AppointmentDetail on lead.CallId equals appoint.CallId into ledapp
      from appoint in ledapp.DefaultIfEmpty() join allocateto in _context.UserMaster on appoint.RelationshipManagerId equals allocateto.UserId into ledAllocateTo
      from allocateto in ledAllocateTo.DefaultIfEmpty()