Mongo DB Connection string from web.config to c# (Collectionname,DB, Connection)

.CS

 private string connectionString = WebConfigurationManager.AppSettings["MongoDbConnectionString"];
        private string mongoDatabase = WebConfigurationManager.AppSettings["MongoDb"];
        private string mongocollection = WebConfigurationManager.AppSettings["Mongocollection"];

        public static string mongoConnKey = "MongoDbConnectionString";
        public static string mongodb = "MongoDb";
        public static string mongocollec = "Mongocollection";

 public string GetSessionData(string transactionID)

        {

            try

            {

                connectionString = ConfigurationManager.AppSettings[mongoConnKey];

                mongoDatabase = ConfigurationManager.AppSettings[mongodb];

                mongocollection = ConfigurationManager.AppSettings[mongocollec];

                var client = new MongoClient(connectionString);

                var _database = client.GetDatabase(mongoDatabase);

                var collection = _database.GetCollection<BsonDocument>(mongocollection);

                var Filter = new BsonDocument("TransactionId", transactionID);

                var result = collection.Find(Filter).ToList();              

                return result.ToString();

            }

            catch (Exception ex)

            {

                return ex.ToString();

            }

        }

Web.config:

   <!--Dev Mongo DB-->

    <add key="MongoDbConnectionString" value="mongodb://testuser:password123@IPaddress:27017/SteveTest" />

    <add key="MongoDb" value="SteveTest" />

    <add key="Mongocollection" value="TestCollection" />

Note : check highliged lines