查找具有少于 n 个子实体的实体

Question

我正在尝试找到一种简单的方法来挑选一个客户服务代表来分配给给定的用户。我有以下型号：

public class Customer
{
    public int Id { get; set; }
    // SNIP
    public virtual Representative Representative { get; set; }
    public bool Active { get; set; }
}

public class Representative
{
    public int Id { get; set; }
    public int MaxActiveCustomers { get; set; }
    // all the customers this representative has interacted with
    public IEnumerable<Customer> Customers { get; set; }
}

我正在努力寻找目前Customers 少于MaxActiveCustomers 建议的任何代表。

我的尝试：

from r in Representatives
where r.MaxActiveCustomers > r.Customers.Count(c => c.Active)
select r

这给了我以下例外：

NotSupportedException: The specified type member 'Customers' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported.

正确的做法是什么？

Answer 1

您已将Customers 定义为IEnumerable<Customer> 类型，EF 不将其视为模型的一部分。将类型更改为ICollection<Customer>。