MySQO Database.cs

using Discord;
using MySql.Data.MySqlClient;
using System;
using System.Collections.Generic;
using System.Linq;

namespace MyBot
{
    class Database
    {
        private string table { get; set; }
        private const string server = "localhost";
        private const string database = "fly_bot_discord";
        private const string username = "root";
        private const string password = "jaron2003";
        private MySqlConnection dbConnection;

        public Database(string table)
        {
            this.table = table;
            MySqlConnectionStringBuilder stringBuilder = new MySqlConnectionStringBuilder();
            stringBuilder.Server = server;
            stringBuilder.UserID = username;
            stringBuilder.Password = password;
            stringBuilder.Database = database;
            stringBuilder.SslMode = MySqlSslMode.None;

            var connectionString = stringBuilder.ToString();

            dbConnection = new MySqlConnection(connectionString);

            dbConnection.Open();
        }

        public MySqlDataReader FireCommand(string query)
        {
            if (dbConnection == null)
            {
                return null;
            }

            MySqlCommand command = new MySqlCommand(query, dbConnection);

            var mySqlReader = command.ExecuteReader();

            return mySqlReader;
        }

        public void CloseConnection()
        {
            if(dbConnection != null)
            {
                dbConnection.Close();
            }
        }

        public static List<String> CheckExistingUser(IUser user)
        {
            var result = new List<String>();
            var database = new Database("fly_bot_discord");

            var str = string.Format("SELECT * FROM fly_bot WHERE user_id = {0}", user.Id);
            var fly_bot_table = database.FireCommand(str);

            while (fly_bot_table.Read())
            {
                var userId = (string)fly_bot_table["user_id"];

                result.Add(userId);
            }

            return result;
        }

    public static string EnterUser(IUser user)
        {
            var database = new Database("fly_bot_discord");

            var str = string.Format("INSERT INTO fly_bot (user_id, username, tokens ) VALUES ({0}, {1}, 100)", user.Id, user.Username);
            var table = database.FireCommand(str);

            database.CloseConnection();

            return null;
        }

    public static List<fly_bot_table> GetUserStatus(IUser user)
        {
            var result = new List<fly_bot_table>();

            var database = new Database("fly_bot_discord");

            var str = string.Format("SELECT * FROM fly_bot WHERE user_id = {0}", user.Id);
            var tableName = database.FireCommand(str);

            while (tableName.Read())
            {
                var userId = (string)tableName["user_id"];
                var userName = (string)tableName["username"];
                var currentTokens = (uint)tableName["tokens"];

                result.Add(new fly_bot_table
                {
                    userid = userId,
                    username = userName,
                    tokens = currentTokens
                });
            }
            database.CloseConnection();

            return result;

        }
    }
}