在AutoMapper

Question

假设我有以下实体框架代码优先模型：

public class Employee {
  [Key]
  public int Id { get; set; }

  public int DepartmentId { get; set; }

  [ForeignKey(nameof(DepartmentId ))]
  public Department Department { get; set; }

  public DateTime EntryDate { get; set; }
}

public class Manager {
  [Key]
  public int Id { get; set; }

  public int DepartmentId { get; set; }

  [ForeignKey(nameof(DepartmentId ))]
  public Department Department { get; set; }
}

public class Department {
  [Key]
  public int Id { get; set; }

  [InverseProperty(nameof(Employee.Department))]
  public virtual ICollection<Employee> Employees { get; set; }

  [InverseProperty(nameof(Manager.Department))]
  public virtual ICollection<Manager> Managers { get; set; }
}

以下DTO对象：

public class MyDto {
  public int ManagerId { get; set; }
  public Employee NewestEmployee { get; set; }  
}

我想使用AutoMapper将管理器列表转换为DTO对象列表。 AutoMapper配置如下：

CreateMap<Manager, MyDto>()
  .ForMember(
    m => m.NewestEmployee,
    opt => opt.MapFrom(
      manager =>
        manager.Department.Employees.OrderBy(employee => employee.EntryDate).FirstOrDefault()))

并且这样称呼：

IEnumerable<Manager> managers = GetAllManagers();
var data = Mapper.Map<IEnumerable<MyDto>>(managers);

虽然这有效，但它会为每个经理向employee表发出单独的SQL语句请求。有没有办法通过只执行一个SQL查询来提高性能（通过更改Entity Framework模型或AutoMapper配置中的某些内容）？