验证登录页面

DBConn.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;
using System.Data;

namespace sixth
{
class DBConn
{
//连接字符串
public static string connStr = "Data Source=.;Initial Catalog=repair;Integrated Security=True;Pooling=False";
public static SqlConnection conn = new SqlConnection(connStr);
}
}

FormLogin.cs

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 System.Data.SqlClient;

namespace sixth
{
public partial class FormLogin : Form
{
public FormLogin()
{
InitializeComponent();
}

private void btnLogin_Click(object sender, EventArgs e)
{
try
{
if (txtUsn.Text.Trim() == "")
{
labMessage.Text ="用户名不能为空!";
txtUsn.Focus();//获取焦点
return;
}
else if (txtPwd.Text.Trim() == "")
{
labMessage.Text ="密码不能为空!";
txtPwd.Focus();
return;
}

//老师说了：下面这种方法会有通过文本框输入SQL语句来恶意损坏数据库的可能，所以用了参数的形式来获取文本框的值！
//string sqlStr = "select userName,passWord from user_info where userName='" + txtUsn.Text.Trim() + "'";

string sqlStr = "select userName,passWord from user_info where userName=@userName";
DataSet ds = new DataSet();
DBConn.conn.ConnectionString = DBConn.connStr;
DBConn.conn.Open();
SqlCommand cmd = new SqlCommand(sqlStr, DBConn.conn);
cmd.Parameters.Add(new SqlParameter("@userName", SqlDbType.VarChar, 50));//添加参数
cmd.Parameters["@userName"].Value = txtUsn.Text;//把用户名文本框里的东西给@userName
SqlDataReader sdr = cmd.ExecuteReader();
if (!sdr.Read())//因为是通过userName查询数据的，所以如果没有读到这条数据，肯定是用户名不存在
{
labMessage.Text = "用户名不存在！请重新输入";
txtUsn.Text = "";//文本框置空
txtPwd.Text = "";
txtUsn.Focus();
}
else if (sdr["passWord"].ToString().Trim() == txtPwd.Text.Trim())
{
labMessage.Text = "恭喜您已成功登录！";
}
else
{
labMessage.Text = "密码错误！请重新输入！";
txtPwd.Text = "";
txtPwd.Focus();
}
}
catch (Exception ex)
{
labMessage.Text = "登录异常：" + ex.Message;
txtUsn.Text = "";
txtPwd.Text = "";
txtUsn.Focus();
}
finally
{
DBConn.conn.Close();//最重要的是要关闭数据库！
}
}

private void btnCancel_Click(object sender, EventArgs e)
{
Application.Exit();//退出
}
}
}