Question

我的类和存储库的结构：

public class Group{
    //fields
}

public class User{
    public UserRole Role {get;set;}
}

public abstract class UserRole{
    //fields
}

public class PersonUserRole:UserRole{
    public Group Group {get;set;}
}

public class ManagerUserRole:UserRole{
    public IList<Group> Groups {get;set;}
}

我遇到问题的一个例子：

public class UserRepository:IUserRepository{
    private readonly ApplicationDbContext _dbContext;
    private readonly DbSet<User> _users;

    public UserRepository(ApplicationDbContext dbcontext)
    {
        _dbContext = dbcontext;
        _users = _dbContext.DomainUsers;
    }

    public User GetBy(int id)
        {
            User type = _users.Include(u => u.Role)
                              .SingleOrDefault(c => c.UserId == id);
            if (typeof(PersonUserRole) == type.Role.GetType())
            {
                return
                    _users.Include(u => u.Role)
                        .ThenInclude(r => (r as PersonUserRole).Groep)
                        .SingleOrDefault(c => c.UserId == id);
            }
            else
            {
                return _users.Include(u => u.Role)
                             .ThenInclude(r => (r as ManagerUserRole).Groups)
                             .SingleOrDefault(c => c.UserId == id);
            }
        }
}

我收到以下错误消息：

消息＆＃34;属性表达式＆＃39; r =＆gt; （r As PersonUserRole）.Group＆＃39;不是有效。表达式应代表属性访问权限：＆＃39; t =＆gt; t.MyProperty＆＃39;

我似乎无法将UserRole类型转换为实际的PersonUserRole类型以包含“组/组”属性。如何包含子类的属性？

Answer 1

更新：从版本2.1开始，EF Core现在自然支持Include on derived types通过强制转换或lambda as / {{1内的Include运算符}重载或ThenInclude string重载。

原始答案（前EF Core 2.1）：

目前不支持加载派生实体导航属性。

作为一种解决方法，您可以使用Loading Related Data中解释的预先加载，显式加载和查询相关实体的组合EF Core文档的一部分：

Include

Answer 2

EntityFramework有一个未解决的问题，与您的问题非常相似：https://github.com/aspnet/EntityFramework/issues/3910

也许你可以尝试他们的建议，但我无法尝试它是否有效：

var o = context.Set<Order>()
    .Where(o => o.Id == 1234)
    .Single();

context.Set<GroupPosition>()
    .Where(x => x.Order == o)
    .Include(x => x.GroupType)
    .Load();

context.Set<SalesPosition>()
    .Where(x => x.Order == o)
    .Include(x => x.Group)
    .Load();

实体框架核心包含子类

2 个答案: