Mongodb C＃：我如何更新嵌入式文档/字典

Question

我有以下用户对象。如何通过mongodb更新构建器为用户添加新的喜欢或不喜欢的朋友。我开始但我无法让它工作。示例代码如下。谢谢

public class User : Entity
{
    public string Name { get; set; }
    public string Email { get; set; }
    public string Password { get; set; }
    public Dictionary<string, Dictionary<string, Friend>> Friends{ get; set; }
}

public class Circle
{
    public string Name { get; set; }
}

以下是mongo json的样子

{
  "Email" : null,
  "Name" : "Nick",
  "Password" : null,
  "Friends" : {
    "Liked" : {
     "WER2343" : {
      "Name" : "Friend 1"
     }
    },
    "Disliked" : {
      "M3222343" : {
       "Name" : "Friend 2"
      }
     }
    },
   "_id" : ObjectId("513b5d84bfeddf1c8091530e")
}

这是我正在努力工作的代码

 public void AddFriend(User self, User friend, string circle)
    {

        IMongoQuery query = Query
            .And(Query<User>.EQ(t => t.Id, self.Id));

        IMongoUpdate update = Update<User>
            .Push(t => t.Friends)

        Collection.FindAndModify(query,null, update);

    }