public string MongoDBFirstTest()
        {

            var mgConnStrBuilder = new MongoConnectionStringBuilder();
            mgConnStrBuilder.Username = "root";
            mgConnStrBuilder.Password = "xxxx";
            mgConnStrBuilder.AddServer("localhost");
            mgConnStrBuilder.Database = "Zuowjdb";

            //链接字符串
            string connectionString = mgConnStrBuilder.ToString(); //"mongodb://root:xxxx@localhost/Zuowjdb";

            //数据库名
            string databaseName = "Zuowjdb";

            //集合名
            string collectionName = "Test";


            //定义Mongo服务
            Mongo mongo = new Mongo(connectionString);

            //链接数据库
            mongo.Connect();

            //获取databaseName对应的数据库，不存在则自动创建
            MongoDatabase mongoDatabase = mongo.GetDatabase(databaseName) as MongoDatabase;

            //获取collectionName对应的集合，不存在则自动创建
            MongoCollection<Document> mongoCollection = mongoDatabase.GetCollection<Document>(collectionName) as MongoCollection<Document>;
            
            try
            {
                //定义一个文档对象，存入两个键值对
                Document doc = new Document();
                doc["ID"] = 1;
                doc["Msg"] = "Hello MongoDB!";

                //将这个文档对象插入集合
                mongoCollection.Insert(doc);

                //在集合中查找键值对为ID=1的文档对象
                //Document docFind = mongoCollection.FindOne(new Document { { "ID", 1 } });

                //输出查找到的文档对象中键“Msg”对应的值，并输出
                // return docFind["Msg"].ToString();

                var docfinds = mongoCollection.Find(new { ID = 1 });
                string result = null;
                foreach (var item in docfinds.Documents)
                {
                    result += item.Get("Msg") + ",";
                }
                mongoCollection.Remove(new { ID = 1 });
                return result;
            }
            finally
            {
                //关闭链接
                mongo.Disconnect();
            }
        }