MySqlHelper

<connectionStrings>
<add name ="connStr" connectionString="server=.;Database=test;Trusted_connection=Yes;connect Timeout=90"/>
</connectionStrings>

using MySql.Data.MySqlClient;
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ADONETTest2
{
    class MySqlHelper
    {
        private static readonly string connstr =
            ConfigurationManager.ConnectionStrings["connstr"].ConnectionString;

        public static MySqlConnection CreateConnection()
        {
            //using (MySqlConnection conn = new MySqlConnection(connstr))
            MySqlConnection conn = new MySqlConnection(connstr);
            conn.Open();
            return conn;
        }

        public static int ExecuteNonQuery(MySqlConnection conn, string sql,
            params MySqlParameter[] parameters)
        {
            using (MySqlCommand cmd = conn.CreateCommand())
            {
                cmd.CommandText = sql;
                /*
                foreach (MySqlParameter p in parameters)
                {
                    cmd.Parameters.Add(p);
                }*/
                cmd.Parameters.AddRange(parameters);
                return cmd.ExecuteNonQuery();
            }
        }

        public static int ExecuteNonQuery(string sql,
            params MySqlParameter[] parameters)
        {
            using (MySqlConnection conn = CreateConnection())
            {
                return ExecuteNonQuery(conn, sql, parameters);
            }
        }

        public static object ExecuteScalar(MySqlConnection conn, string sql,
            params MySqlParameter[] parameters)
        {
            using (MySqlCommand cmd = conn.CreateCommand())
            {
                cmd.CommandText = sql;
                cmd.Parameters.AddRange(parameters);
                return cmd.ExecuteScalar();
            }
        }

        public static object ExecuteScalar(string sql,
           params MySqlParameter[] parameters)
        {
            using (MySqlConnection conn = CreateConnection())
            {
                return ExecuteScalar(conn, sql, parameters);
            }
        }

        public static DataTable ExecuteQuery(MySqlConnection conn, string sql,
           params MySqlParameter[] parameters)
        {
            DataTable table = new DataTable();
            using (MySqlCommand cmd = conn.CreateCommand())
            {
                cmd.CommandText = sql;
                cmd.Parameters.AddRange(parameters);
                using (MySqlDataReader reader = cmd.ExecuteReader())
                {
                    table.Load(reader);                    
                }
            }
            return table;
        }

        public static DataTable ExecuteQuery(string sql,
           params MySqlParameter[] parameters)
        {
            using (MySqlConnection conn = CreateConnection())
            {
                return ExecuteQuery(conn, sql, parameters);
            }
        }
    }
}