c# – RavenDB Map / Reduce over属性是一个列表

我有一个对象：

public class User : IIdentifiable
{
    public User(string username)
    {
        Id = String.Format(@"users/{0}",username);
        Favorites = new List<string>();
    }

    public IList<string> Favorites { get; protected set; }

    public string Id { get; set; }
}

我想要做的是在所有用户中获取Map / Reduce收藏夹属性.像这样的东西(但这显然不起作用)：

Map = users => from user in users
                from oil in user.Favorites
                select new { OilId = oil,Count = 1 };
 Reduce = results => from result in results
                     group result by result.OilId into g
                     select new { OilId = g.Key,Count = g.Sum(x => x.Count) };

例如,如果User1有收藏夹1,2,3,而用户2有收藏夹1,那么这应该返回{{OilId = 3,Count = 1},{OilId = 2,Count = 2},{OilId = 1,Count = 2}}

当前代码产生异常：System.NotSupportedException：不支持节点：调用

我觉得我很亲密.有帮助吗？