[MongoDB]对数组操作

using MongoDB.Bson;
using MongoDB.Driver;
using MongoDB.Driver.Builders;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Wolfy.Mongodb
{
    class Program
    {
        static void Main(string[] args)
        {
        }
    }
    class MongoHelper
    {
        private static readonly string _db = "";
        private static readonly string _col = "";
        private static readonly string _ip = "";
        private static readonly string _user = "";
        private static readonly string _pwd = "";
        private static readonly string _connStr = string.Format("mongodb://{0}:{1}@{2}:27017/{3}", _user, _pwd, _ip, _db);

        /// <summary>
        /// 为某个userId添加friend，如果数组中不存在则添加
        /// </summary>
        /// <param name="userId"></param>
        /// <param name="friendId"></param>
        /// <returns></returns>
        public static bool UpdateOrInsert(string userId, string friendId)
        {
            var col = GetCollection();
            var query = new QueryDocument { { "userId", userId }, new QueryDocument { { "$nin", new BsonArray().Add(friendId) } } };
            var update = Update.Push("friends", friendId).Inc("count", 1);
            return col.Update(query, update, UpdateFlags.None).Ok;
        }

        private static MongoCollection<BsonDocument> GetCollection()
        {
            MongoClient client = new MongoClient(_connStr);
            MongoServer server = client.GetServer();
            var db = server.GetDatabase(_db);
            var col = db.GetCollection(_col);
            return col;
        }
        /// <summary>
        /// 从属性中移除好友
        /// </summary>
        /// <param name="userId"></param>
        /// <param name="friendId"></param>
        /// <returns></returns>
        public static bool RemoveFriend(string userId, string friendId)
        {
            var col = GetCollection();
            var query = new QueryDocument { { "userId", userId } };
            MongoDB.Driver.Builders.UpdateBuilder builder = new MongoDB.Driver.Builders.UpdateBuilder();
            builder.Pull("friends", friendId);
            return col.Update(query, builder, UpdateFlags.None).Ok;
        }
        /// <summary>
        /// 更新字段值
        /// </summary>
        /// <param name="userId"></param>
        /// <param name="dic"></param>
        /// <returns></returns>
        public static bool UpdateFields(string userId, Dictionary<string, object> dic)
        {
            var col = GetCollection();
            var query = new QueryDocument { { "userId", userId } };
            MongoDB.Driver.Builders.UpdateBuilder builder = new MongoDB.Driver.Builders.UpdateBuilder();
            foreach (var item in dic.Keys)
            {
                builder.Set(item, BsonValue.Create(dic[item]));
            }
            builder.Set("dt", DateTime.Now);
            return col.Update(query, builder, UpdateFlags.Upsert).Ok;
        }
    }
}