NewLibrary/Book_manger/Sql/Form51.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Sql
{
    public partial class Form51 : Form
    {
        public Form51()
        {
            InitializeComponent();
        }

        private void button4_Click(object sender, EventArgs e)
        {
            textBox1.Text = null;
        }

        private void button5_Click(object sender, EventArgs e)
        {
            textBox2.Text = null;
        }

        private void button6_Click(object sender, EventArgs e)
        {
            textBox3.Text = null;
        }

        private void button3_Click(object sender, EventArgs e)
        {
            if (textBox1.Text == "" || textBox2.Text == "" || textBox3.Text == "")
            {
                MessageBox.Show("不能有空项", "提示", MessageBoxButtons.OK, MessageBoxIcon.Warning);
            }
            else 
            {

                string sql = "select * from Student where Name='" + textBox1.Text + "'";//查询学生表中姓名等于第一个框中所填的数据的学生行
                Dao dao = new Dao();
                IDataReader dr = dao.read(sql);
                dr.Read();                      //这一步非常重要，缺一不可，用于读取数据
                string a;
                a = dr["Password"].ToString();//读取对应姓名的学生的密码是否和第二个框中的旧密码一致
                if ( textBox2.Text!=a)
                {
                    MessageBox.Show("旧密码输入错误！");
                }
                else
                {
                    string sq = "update Student set Password=" + textBox3.Text + " where Name='" + textBox1.Text + "'";//如果写的旧密码正确，那么执行更新操作
                   // MessageBox.Show(sq);
                    Dao da = new Dao();
                    da.Execute(sq);    //执行更新对应用户名密码的功能
/*                    sq = "update Student set Password='" + textBox2.Text + "'";       
                    da.Execute(sq);*/
                    MessageBox.Show("修改密码成功");
                    Close();
                }

            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}