如何使用 EF 和 linq 获取带有嵌套信息的实体

Question

我有 3 个相关的表。员工、亲戚、RelationTypeCatalog。关系是IX_Relatives_EmployeeId和IX_Relatives_RelationTypeCatalogId。

如何使用 EF 编写此查询？

我正在尝试从一名员工那里获取信息，该员工的亲属名单以及他们之间的关系类型。到目前为止，我已经尝试了这些选项：

public async Task<Employee> GetEmployee(int id)
{
//(1) tried this
return await _context.Employees
            .Include(emp=> emp.Relatives.Select(rel=> 
             rel.RelationTypeCatalog))
            .FirstOrDefaultAsync(emp=>emp.Id == id);


}
//(2) also tried this...
public async Task<Employee> GetEmployee(int id)
{
var  test = (from e in _context.Employees
                        join re in _context.Relatives
                        on e.Id equals re.EmployeeId
                        join t in _context.RelationTypes
                        on re.RelationTypeCatalogId equals t.Id
                        where e.Id == id
                        select e).FirstOrDefaultAsync();

            return await test;
}

这是 SQL

查询的样子

SELECT * 
from sagrha.employees 
inner join sagrha.relatives
on employees.Id = relatives.EmployeeId
inner join sagrha.relationtypes
on relatives.RelationTypeCatalogId= sagrha.relationtypes.Id;

我正在寻找类似于

的 json 结果

{
    "id": 1,
    "name": "Homero",
    "gender": "male",
    "relatives": [ 
    "Name":"Bart"
    "RelationType":"Child"
    ]
}

Answer 1

尝试使用 Include 和 Then Include，如下所示：

return await _context.Employees
            .Include(emp=> emp.Relatives).ThenInclude(rel => rel.RelationTypeCatalog)
            .FirstOrDefaultAsync(emp=>emp.Id == id);