C#链接MySQL

//需要添加引用MySql.Data.dll
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using MySql.Data.MySqlClient;//导入用MySql的包
namespace LinkMysql
{
    public partial class Form1 : Form
    {
        TestMysql.SQLHelper helper = new TestMysql.SQLHelper();
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            string name = "";
            string sql = string.Format("select * from stuinfo");
            DataTable dt = helper.Selectinfo(sql);
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                //从数据库得到stuname 字段的值
                name += (string)dt.Rows[i]["stuname"] + "\r\n";

            }
            //把得到的值放到文本框中
            this.textBox1.Text = name;


        }



        private void btnAdd_Click(object sender, EventArgs e)
        {
            string sql = string.Format("insert into userinfo values('{0}','{1}')", "root", "admin");
            int i = helper.AddDelUpdate(sql);
            if (i > 0)
            {
                MessageBox.Show("增加成功");

            }

        }

        private void btnExit_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }
    }
}


namespace TestMysql
{
    public class DBHelper
    {
        /// <summary>
        /// 得到连接对象
        /// </summary>
        /// <returns></returns>
        public MySqlConnection GetConn()
        {
            MySqlConnection mysqlconn = new MySqlConnection("Database='" + "test" + "';Data Source='" + "localhost" + "';User Id='" + "root" + "';Password='" + "admin" + "'");
            return mysqlconn;
        }
    }


    public class SQLHelper : DBHelper
    {
        /// <summary>
        /// 查询操作
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public DataTable Selectinfo(string sql)
        {
            MySqlConnection mysqlconn = null;
            MySqlDataAdapter sda = null;
            DataTable dt = null;
            try
            {
                mysqlconn = base.GetConn();

                sda = new MySqlDataAdapter(sql, mysqlconn);
                dt = new DataTable();
                sda.Fill(dt);

                return dt;
            }
            catch (Exception)
            {

                throw;
            }

        }

        /// <summary>
        /// 增删改操作
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <returns>执行后的条数</returns>
        public int AddDelUpdate(string sql)
        {

            MySqlConnection conn = null;
            MySqlCommand cmd = null;

            try
            {
                conn = base.GetConn();
                conn.Open();
                cmd = new MySqlCommand(sql,conn);
                int i = cmd.ExecuteNonQuery();

                return i;

                conn.Close();
            }
            catch (Exception)
            {
                
                throw;
            }
        
        }



    }
}