如何使用c＃* Lambda *连接3个对象并返回t1。*和t2和t3中选定的cols

Question

C＃Lambda只是请。否Linq - 查询样式。

寻找关于如何连接3个对象的策略，这些对象将输出为以下SQL（c＃lambda的最终目标）：

SELECT t1.*, t2.name pet_name, t3.name teacher_name
FROM user_profile t1
    INNER JOIN pet_profile t2 on t1.pet_id = t2.pet_id
    INNER JOIN pet_teacher t3 on t1.pet_teacher_id = t3.pet_teacher_id

user_profile 列：

1. USER_ID
2. user_fullname
3. pet_id
4. pet_teacher_id

pet_profile 列：

1. pet_id
2. 名称

pet_teacher 列：

1. pet_teacher_id
2. 名称

我现在拥有的是使用此查询加入2个对象：

IQueryable<UserProfile> query = dataContext.UserProfile;

var queryTest = query
    .Join(dataContext.PetProfile,
        UserProfile => UserProfile.pet_id,
        t2 => t2.pet_id,
        (UserProfile, t2) => new { UserProfile, PetName = t2.name });

这将生成此SQL：

SELECT UserProfile.user_id,
    UserProfile.user_fullname,
    UserProfile.pet_id,
    UserProfile.pet_teacher_id,
    t2.name PetName
FROM user_profile UserProfile
    INNER JOIN pet_profile t2 on UserProfile.pet_id = t2.pet_id

[Q1：]如何加入第3张表 pet_teacher

[Q2：]如何手动执行user_profile的所有字段：

var UserAndPet = query.Select(o => 
        new { o.UserProfile.user_id, 
            o.UserProfile.user_fullname,
            o.UserProfile.pet_id, 
            o.UserProfile.pet_teacher_id, 
            o.UserProfile.PetName, 
            o.UserProfile.TeacherName  }
    ).ToList();
enter code here

Answer 1

对于第3张表

var queryTest = query
    .Join(dataContext.PetProfile,
        UserProfile => UserProfile.pet_id,
        t2 => t2.pet_id,
        (UserProfile, t2) => new { UserProfile, PetName = t2.name })
    .Join(datacontext.PetTeacher,
          x=>x.UserProfile.pet_teacher_id,
          y=>y.pet_teacher_id,(x,y)=>new {x.UserProfile,x.petname,x.teacherName})

对于第二个问题，如果所有列都来自同一个表

，则可以执行此操作

var UserAndPet = query.Select(o =>o).ToList();