c# - 获取嵌套实体的数量

Question

我正在尝试获取 LINQ 中特定州的员工数。

我有这样的东西:

States
     |
     Cities
          |
          Posts
              |
              Employees

如何通过手头选定的 State 获取 Employees 计数？

我的实体是:

public class Province : EntityBase
{
    public String ProvinceName { get; set; }
    public virtual IList<City> Cities { get; set; }
}

public class City : EntityBase
{
    public String CityName { get; set; }

    public virtual Province Province { get; set; }
    public virtual IList<Post> ElectricPosts { get; set; }
}

public class Post : EntityBase
{
    public String PostName { get; set; }
    public virtual City City { get; set; }
    public virtual IList<Employee> Employees { get; set; }
}

public class Employee : Person
{
    public virtual String FirstName { get; set; }
    public virtual String SureName { get; set; }
    public virtual Post ElectricPost { get; set; }
}

编辑: 有趣的是，我可以毫无问题和异常地计算帖子，但是当我想尝试@HamletHakobyan 帖子中的方法时，我收到 NullReferenceException 并且我不知道为什么？

Answer 1

我不确定，但试试这个:

var state = ((IObjectContextAdapter)context)
            .ObjectContext
            .CreateObjectSet<Province>("States") as ObjectQuery<Province>;
            // States is entitySetName

int count = state.Cities.Include("ElectricPosts.Employees")
                    .SelectMany(c => c.Posts)
                    .SelectMany(p => p.Employees)
                    .Count();