F2V1

using MySql.Data.MySqlClient;
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;

namespace WindowsFormsApp1
{
    public partial class Form2 : Form
    {
        private string account = "";

        public DataTable GetDataTable(string sql)
        {

            MySqlConnection conn = new MySqlConnection("server=localhost;user id=root;password=123456;database=jian");
            MySqlCommand cmd = conn.CreateCommand();//命令对象（用来封装需要在数据库执行的语句）
            cmd.CommandText = sql;//设置sql文本

            //第一种方式，用数据适配器
            MySqlDataAdapter sda = new MySqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            sda.Fill(dt);//这里也可以把数据查询结果填充到DataSet中
            return dt;

        }


        /// <summary>
        /// 建立数据库连接.
        /// </summary>
        /// <returns>返回MySqlConnection对象</returns>
        public MySqlConnection getmysqlcon()
        {
            try
            {
                string M_str_sqlcon = "server=127.0.0.1;user=root;password=123456;database=jian"; //根据自己的设置
                MySqlConnection myCon = new MySqlConnection(M_str_sqlcon);
                return myCon;
            }
            catch (Exception ex) {
                MessageBox.Show(ex.ToString());
                return null;
            }
        }
        
        /// <summary>
        /// 创建一个MySqlDataReader对象
        /// </summary>
        /// <param name="M_str_sqlstr">SQL语句</param>
        /// <returns>返回MySqlDataReader对象</returns>
        public MySqlDataReader getmysqlread(string M_str_sqlstr)
        {
            MySqlConnection mysqlcon = this.getmysqlcon();
            MySqlCommand mysqlcom = new MySqlCommand(M_str_sqlstr, mysqlcon);
            mysqlcon.Open();
            MySqlDataReader mysqlread = mysqlcom.ExecuteReader();
            return mysqlread;
        }

        public Form2()
        {
            InitializeComponent();
        }
        public Form2(string account)
        {
            this.account = account;
            InitializeComponent();
        }

        private void button4_Click(object sender, EventArgs e)
        {
            this.Hide();
        }

        private void Form2_Load(object sender, EventArgs e)
        {
            string sql = string.Format("select msg from updatemsg where account = '{0}'  ", this.account);
            DataTable result = GetDataTable(sql);
            comboBoxMsg.DisplayMember = "msg";
            comboBoxMsg.ValueMember = "msg";
            comboBoxMsg.DataSource = result;
            //string sql = string.Format("select msg from updatemsg where account = '{0}'  ", this.account);
            //MySqlDataReader result = getmysqlread(sql);
            //while (result.Read()) {
            //    comboBoxMsg.Items.Add(result[0].ToString());
            //}
        }

        private void button1_Click(object sender, EventArgs e)
        {

            if (comboBoxMsg.Text != null) {
                string sql = string.Format("UPDATE updatemsg SET msg='{0}' where account = '{1}' and msg = '{2}' ", textBoxUpdate.Text, this.account,comboBoxMsg.Text);

                MessageBox.Show(sql);
                MySqlDataReader result = getmysqlread(sql);
            }
        }

        private void Form2_VisibleChanged(object sender, EventArgs e)
        {
            string sql = string.Format("select msg from updatemsg where account = '{0}'  ", this.account);
            DataTable result = GetDataTable(sql);
            comboBoxMsg.DisplayMember = "msg";
            comboBoxMsg.ValueMember =  "msg";
            comboBoxMsg.DataSource = result;
            //while (result.Read())
            //{
            //    comboBoxMsg.Items.Add(result[0].ToString());
            //}
        }
    }
}