login.cs

利用vs2008+sql2000开发的小型学生信息系统

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace StudentInfoMS
{
    public partial class login : Form
    {
        public login()
        {
            InitializeComponent();
        }

        private void btn_ok_Click(object sender, EventArgs e)
        {
            string connstr = "Data Source=localhost;Initial Catalog=mystuInfoDB;Integrated Security= true;";
            //返回用户数量，如果为0，则用户id不存在
            string cmduserid = "select count(userid) from login where userid='" + textBox1.Text.ToString() + "'";
            //返回正确用户密码
            string cmdstr = "select password from login where userid='" + textBox1.Text.ToString() + "'";
            SqlCommand cmd=new SqlCommand();
            SqlConnection mysqlconnection = new SqlConnection(connstr);

            if (textBox1.Text.Length==0)
            {
                MessageBox.Show("请输入您的用户名！", "注意", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                textBox1.Focus();
            }
            else if (textBox2.Text.Length == 0)
            {
                MessageBox.Show("请输入您的密码！", "注意", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                textBox2.Focus();
            }
            else
            {
                try
                {
                    cmd = mysqlconnection.CreateCommand();
                    cmd.CommandText=cmduserid;
                    mysqlconnection.Open();
                    int length=int.Parse(cmd.ExecuteScalar().ToString());//返回userid的长度
                    mysqlconnection.Close();
                    if (length == 0)//如果userid为0 则用户名不存在
                    {
                        MessageBox.Show("用户名不存在，请重新输入！", "注意", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                        textBox1.Focus();
                        textBox2.Text = null;
                    }
                    else{
                        cmd.CommandText = cmdstr;
                        mysqlconnection.Open();
                        string pswd=cmd.ExecuteScalar().ToString().Trim();
                        mysqlconnection.Close();
                         if (textBox2.Text.ToString().Trim().Equals(pswd))
                         {
                            MessageBox.Show("Welcome "+textBox1.Text.ToString().Trim()+"！");
                            Form1 stuinfoms=new Form1();
                            stuinfoms.Show();
                            this.Hide();
                         }
                         else
                         {
                            MessageBox.Show("密码不正确,请重新输入","",MessageBoxButtons.OK,MessageBoxIcon.Stop);
                            textBox2.Text=null;
                            textBox2.Focus();
                         }
                       }
                }
                catch (Exception ex)
                {
                    MessageBox.Show("连接数据库出错", "ERROR", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
                finally
                {
                    mysqlconnection.Close();
                }
            }

        }

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

        private void btn_reset_Click(object sender, EventArgs e)
        {
            textBox1.Text = null;
            textBox2.Text = null;
            textBox1.Focus();
        }

    }
}