Entity framework LINQ到实体-唯一左外部联接场景

我正试图用Linq to Entity语法编写以下左外连接场景，但我一辈子都搞不清楚如何实现它以下是我试图最终实现的工作SQL：

选择*
来自学生的 在ps.StudentId=s.StudentId和ps.ParentId='6D279F72-2623-459F-B701-5C77C52BA52F'上左键连接家长学生ps

其中s.TenantId=3，s.FamilyId='2883312-46eb-4a54-9132-8a7c8037cec5'

粗体突出显示的部分是我摔倒的地方。。。我希望学生返回，无论数据库中是否有任何ParentStudent记录

以下是我的最新LINQ to Entity代码，该代码不起作用：

    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();
    }

公共ICollection GetParentStudents（Guid FamilyId，Guid ParentId） { var query=来自DataContext.Students中的s 来自s.ParentStudents.DefaultIfEmpty（）中的ps 其中s.TenantId==CurrentUser.TenantId&&s.FamilyId==FamilyId&&ps.ParentId==ParentId 选择新的ParentStudentListing{StudentId=s.StudentId，FirstName=s.FirstName，MiddleName=s.MiddleName，LastName=s.LastName，RelationshipId=ps.RelationshipId，ParentStudentId=ps.ParentStudentId，isAllowedToPickUp=ps.isEmergency=ps.isEmergency，isLiveIn=ps.isLiveIn，ParentId=ps.ParentId}； 返回query.ToList（）； } 除非数据库中存在非预期结果的ParentStudent记录，否则此代码不会返回学生。我想把学生带回来，不管是否有家长学生记录，但如果有家长学生记录，我希望这些记录与学生记录结合起来

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谢谢大家!

这是我第一次尝试LINQ连接：

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 };

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引用自。

感谢Joe提供的额外帮助。。。。这并没有让我达到目的，但我最终还是让它运行起来了。以下是工作代码：

    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();
    }

公共ICollection GetParentStudents（Guid FamilyId，Guid ParentId） { var query=来自DataContext.Students中的s 在DataContext.ParentStudents中加入ps 在新的{s.StudentId，ParentId=ParentId} 等于新的{ps.StudentId，ps.ParentId}到ps_join 从ps_join.DefaultIfEmpty（）中的ps 其中s.TenantId==CurrentUser.TenantId&&s.FamilyId==FamilyId 选择新的ParentStudentListing{StudentId=s.StudentId，FirstName=s.FirstName，MiddleName=s.MiddleName，LastName=s.LastName，RelationshipId=ps.RelationshipId，ParentStudentId=ps.ParentStudentId，isAllowedToPickUp=ps.isEmergency=ps.isEmergency，isLiveIn=ps.isLiveIn，ParentId=ps.ParentId}； 返回query.ToList（）； }

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Joe你的回答同样有用！再次感谢！