public class MongoDb

    {

        //方式一

        //private static readonly string connStr = "mongodb://myAdmin:123456@localhost";

        //private static readonly string dbName = "myTest";

        //方式二（myTestAdmin用户只可访问数据库myTest）

        private static readonly string connStr = "mongodb://myTestAdmin:123456@localhost/myTest";

        private static IMongoDatabase db = null;

        private static readonly object lockHelper = new object();

        private MongoDb() { }

        public static IMongoDatabase GetMongoDb()

        {

            if (db == null)

            {

                lock (lockHelper)

                {

                    if (db == null)

                    {

                        //方式一

                        //var client = new MongoClient(connStr);

                        //db = client.GetDatabase(dbName);

                        //方式二（myTestAdmin用户只可访问数据库myTest）

                        var url = new MongoUrl(connStr);

                        MongoClientSettings mcs = MongoClientSettings.FromUrl(url);

                        mcs.MaxConnectionLifeTime = TimeSpan.FromMilliseconds();

                        var client = new MongoClient(mcs);

                        db = client.GetDatabase(url.DatabaseName);

                    }

                }

            }

            return db;

        }

    }

class Program

    {

        static void Main(string[] args)

        {

            IMongoDatabase db = MongoDb.GetMongoDb();

            var collection = db.GetCollection<BsonDocument>("userInfo");            

            //插入

            var document = new BsonDocument

            {

                { "name", "Liming" },

                { "age", "" },

                { "score", new BsonDocument

                    {

                        { "yuwen",  },

                        { "shuxue",  },

                        { "yingyu",  }

                    }}

            };

            collection.InsertOne(document);            

            Console.ReadKey();

        }

    }

class Program

    {

        static void Main(string[] args)

        {

            IMongoDatabase db = MongoDb.GetMongoDb();

            var collection = db.GetCollection<BsonDocument>("userInfo");            

            //查询

            var document = collection.Find(new BsonDocument()).FirstOrDefault();

            Console.WriteLine(document.ToString());

            Console.ReadKey();

        }

    }

class Program

    {

        static void Main(string[] args)

        {

            IMongoDatabase db = MongoDb.GetMongoDb();

            var collection = db.GetCollection<BsonDocument>("userInfo");            

            //更新

            var filter = Builders<BsonDocument>.Filter.Eq("age", "");

            var update = Builders<BsonDocument>.Update.Set("age", "");

            collection.UpdateOne(filter, update);

            Console.ReadKey();

        }

    }

 class Program

    {

        static void Main(string[] args)

        {

            IMongoDatabase db = MongoDb.GetMongoDb();

            var collection = db.GetCollection<BsonDocument>("userInfo");            

            //删除

            var filter1 = Builders<BsonDocument>.Filter.Eq("age", "");

            collection.DeleteOne(filter1);

            Console.ReadKey();

        }

    }