来自TPH继承中的子类型的LINQ .Include()属性

Question

我在Entity Framework中使用每层次表(TPH)继承.现在我希望得到一个列表 - 在这个例子中 - 部门可以是子类型.我希望集合中的项目包含自己的自定义属性,而不仅仅是基本模型的属性.

我怎样才能做到这一点？

public class Department
{
    public Department()
    {
        DepartmentType = this.GetType.Name;
    }
    public int Id {get; set;}
    public string DepartmentType {get; set;}
}

public class Finance : Department
{
    public virtual Manager Manager {get; set;}
}

public class Sports : Department
{
    public virtual Coach Coach {get; set;}
}


// This obviously crashes instantly
// How can I include Manager if type is Finance and Coach if type is Sports?
context.Departments
        .Include(c => (c is Finance) ? c.Manager : null)
        .Include(c => (c is Sports) ? c.Coach : null);

我甚至试图返回IEnumerable<object>并为每个子类型添加一个多态方法,如下所示:

public class Sports : Department
{
    public Coach Coach {get; set;}

    public object Export()
    {
        return new 
        {
            this.Id,
            this.DepartmentType,
            this.Coach
        }
    }
}

然后做这样的事情:

context.Departments.Select(c => c.Export())

但这也不起作用.

期望的JSON用法

[
    { Id: 1, DepartmentType: "Finance", Manager: { Name: "John" } },
    { Id: 2, DepartmentType: "Finance", Manager: { Name: "Harold" } },
    { Id: 3, DepartmentType: "Sport", Coach: { Name: "Fred", SportType: "Soccer" } },
    { Id: 4, DepartmentType: "Finance", Manager: { Name: "Hank" } },
    { Id: 5, DepartmentType: "Sport", Coach: { Name: "Mark", SportType: "Football" } }
]

Answer 1

通过这种方式，您可以找到财务和体育部门并包括它们的属性：

var financeDeparments = context.Departments.OfType<Finance>().Include(p => p.Manager).ToList();
var sportDepartments = context.Departments.OfType<Sports>().Include(p => p.Coach).ToList();