Lambda语法将多个引用表连接到主表

Question

我有3个表:

• Users:(Id, FirstName, LastName, DepartmentId, LocationId)
• Departments:(Id, DepartmentName)
• Locations: (Id, LocationName)

如何使用lambda表达式将Department.Id连接到User.DepartmentId和Location.Id连接到User.LocationId?

我被卡住了目前与1连接。我试着去研究这个问题，但是我看到的结果与多对多的关系有关。

var userJoin = _db.Users
.Join(_db.Departments, 
user => user.DepartmentId, 
dept=> dept.Id, 
(l, r) => new { l, r })
.Select(m => new UserModel()
{
// Map
}).ToList();

Answer 1

您有几个选择:

使用导航属性。它会更简单，看起来像这样

context.Users.Include(x=>x.Department)
.Include(x=>x.Location)
.ToList()

使用加入

context.Users.Join(context.Departments, x=>x.DepartmentId, x=>x.Id, (user, department) => new
{
User = user, 
Department = department
})
.Join(context.Locations, x=>x.User.LocationId, x=>x.Id, (userDepartment, location) => new
{
User = userDepartment.User, 
Department = userDepartment.Department,
Location = location
})
.ToList()