尋找一種更好的方法來通過 ID 獲取項目集合

Question

我有一個非常標准的設置，部門和員工之間有多對多的關系。

Departments
---------------
DepartmentID
Name

Employees
---------------
EmployeeID
Name

DepartmentEmployees
-------------------
DepartmentID
EmployeeID

給定一個部門，我想返回該部門的員工列表。 這是我所擁有的：

public partial class Department
{
    public List<Employee> GetEmployees()
    {
        int[] employeeIds = MyDBDataContext.DepartmentEmployees.
                            Where(de => de.DepartmentID == this.DepartmentID).
                            Select(de => de.EmployeeID.Value).ToArray();

        List<Employee> employees = (from x in MyDBDataContext.Employees
                                    where employeeIds.Contains(x.EmployeeID)
                                    select x).ToList();

        return employees;
    }
}

這很好用，但我不喜歡進行兩次數據庫調用。 LINQ 還有其他方法嗎？

Answer 1

為什么不使用聯接？

var employees = (from e in MyDBDataContext.Employees
                 join de in MyDBDataContext.DepartmentEmployees
                     on e.EmployeeID equals de.EmployeeID
                 where de.DepartmentID == this.DepartmentID
                 select e).ToList();