LINQ到实体 - 唯一的左外部加入Scenerio

我想写下面的左外部在Linq中加入scenerio到实体的语法，我不能为我的生活弄清楚如何将它拉下来... 这里是工作SQL，我想最终达到：LINQ到实体 - 唯一的左外部加入Scenerio

SELECT *
学生小号 LEFT JOIN ParentStudents PS开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'

以粗体突出显示的部分是我跌倒的地方...我希望学生无论数据库中是否存在ParentStudent记录都会返回。

这是我最新的LINQ到实体代码不起作用：

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(); 
    }

此代码不带回来的学生除非有这不是想要的结果数据库ParentStudent记录。无论是否有ParentStudent记录，我都希望带回学生，但如果有ParentStudent记录，我希望那些与学生记录结合起来...

谢谢！

来源

2012-09-08 Drew Auman

感谢乔的补充帮助....这并不完全让我在那里，但我终于得到它运行。这里是工作代码：

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(); 
    }

来源

2012-09-08 20:16:47

乔你回答同样有帮助！再次感谢！ –

这是我在LINQ第一次尝试加入：

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 };

从here引用。

来源

2012-09-08 12:34:54

LINQ到实体 - 唯一的左外部加入Scenerio

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