LINQ到實體 - 唯一的左外部加入Scenerio

Question

我想寫下面的左外部在Linq中加入scenerio到實體的語法，我不能爲我的生活弄清楚如何將它拉下來... 這裏是工作SQL，我想最終達到：

SELECT *
學生小號 LEFT JOIN ParentStudents PS開ps.StudentId = s.StudentId AND ps.ParentId =「6D279F72-2623-459F -B701-5C77C52BA52F'

其中s.TenantId = 3 AND s.FamilyId ='28833312-46eb -4a54-9132-8a7c8037cec5'

以粗體突出顯示的部分是我跌倒的地方...我希望學生無論數據庫中是否存在ParentStudent記錄都會返回。

這是我最新的LINQ到實體代碼不起作用：

public ICollection<ParentStudentListing> GetParentStudents(Guid FamilyId, Guid ParentId) 
    { 
     var query = from s in DataContext.Students 
        from ps in s.ParentStudents.DefaultIfEmpty() 
        where s.TenantId == CurrentUser.TenantId && s.FamilyId == FamilyId && ps.ParentId == ParentId 
        select new ParentStudentListing { StudentId = s.StudentId, FirstName = s.FirstName, MiddleName = s.MiddleName, LastName = s.LastName, RelationshipId = ps.RelationshipId, ParentStudentId = ps.ParentStudentId, isAllowedToPickUp = ps.isAllowedToPickUp, isEmergency = ps.isEmergency, isLiveIn = ps.isLiveIn, ParentId = ps.ParentId }; 

     return query.ToList(); 
    } 

此代碼不帶回來的學生除非有這不是想要的結果數據庫ParentStudent記錄。無論是否有ParentStudent記錄，我都希望帶回學生，但如果有ParentStudent記錄，我希望那些與學生記錄結合起來...

謝謝！

Answer 1

感謝喬的補充幫助....這並不完全讓我在那裏，但我終於得到它運行。這裏是工作代碼：

public ICollection<ParentStudentListing> GetParentStudents(Guid FamilyId, Guid ParentId) 
    { 
     var query = from s in DataContext.Students 
        join ps in DataContext.ParentStudents 
          on new { s.StudentId, ParentId = ParentId } 
         equals new { ps.StudentId, ps.ParentId } into ps_join 
        from ps in ps_join.DefaultIfEmpty() 
        where s.TenantId == CurrentUser.TenantId && s.FamilyId == FamilyId 
        select new ParentStudentListing { StudentId = s.StudentId, FirstName = s.FirstName, MiddleName = s.MiddleName, LastName = s.LastName, RelationshipId = ps.RelationshipId, ParentStudentId = ps.ParentStudentId, isAllowedToPickUp = ps.isAllowedToPickUp, isEmergency = ps.isEmergency, isLiveIn = ps.isLiveIn, ParentId = ps.ParentId }; 

     return query.ToList(); 
    } 

Answer 2

這是我在LINQ第一次嘗試加入：

var query = from s in DataContext.Students 
      join ps in s.ParentStudents on ps.ParentId equals s.ParentId into ps 
      from ps in ps.DefaultIfEmpty() 
      where s.TenantId == CurrentUser.TenantId && s.FamilyId == FamilyId     
      select new ParentStudentListing { StudentId = s.StudentId, FirstName = s.FirstName, MiddleName = s.MiddleName, LastName = s.LastName, RelationshipId = ps.RelationshipId, ParentStudentId = ps.ParentStudentId, isAllowedToPickUp = ps.isAllowedToPickUp, isEmergency = ps.isEmergency, isLiveIn = ps.isLiveIn, ParentId = ps.ParentId }; 

從here引用。