Linq左連接需要的語法校正

Question

我有問題找出多個連接中左外連接的Linq語法。我想在RunLogEntry Table上進行左連接，因此我得到了與此表匹配的記錄以及所有服務條目。

有人能糾正我的snytax嗎？

var list = (from se in db.ServiceEntry 
    join u in db.User on se.TechnicianID equals u.ID 
    join s in db.System1 on se.SystemID equals s.ID 
    join r in db.RunLogEntry on se.RunLogEntryID equals r.ID 
    where se.ClosedDate.HasValue == false 
    where se.ClosedDate.HasValue == false 
     && se.Reconciled == false 
    orderby se.ID descending 
    select new ServiceSearchEntry() 
    { 
     ID = se.ID, 
     ServiceDateTime = se.ServiceDateTime, 
     Technician = u.FullName, 
     System = s.SystemFullName, 
     ReasonForFailure = se.ReasonForFailure, 
     RunDate = r.RunDate 
    }) 
    .Skip((page - 1) * PageSize); 

Answer 1

使用上r的.DefaultIfEmpty方法執行左連接：

var list = (from se in db.ServiceEntry 
    join r in db.RunLogEntry on se.RunLogEntryID equals r.ID into joinRunLogEntry 
    from r2 in joinRunLogEntry.DefaultIfEmpty() 
    join u in db.User on se.TechnicianID equals u.ID 
    join s in db.System1 on se.SystemID equals s.ID 
    where se.ClosedDate.HasValue == false 
    where se.ClosedDate.HasValue == false 
     && se.Reconciled == false 
    orderby se.ID descending 
    select new ServiceSearchEntry() 
    { 
     ID = se.ID, 
     ServiceDateTime = se.ServiceDateTime, 
     Technician = u.FullName, 
     System = s.SystemFullName, 
     ReasonForFailure = se.ReasonForFailure, 
     RunDate = (r2 == null ? (DateTime?)null : r2.RunDate) 
    }) 
    .Skip((page - 1) * PageSize);