基于数据库的C#用户登录程序

这篇文章只是部分代码，是将一个项目拆开了的，避免放在一块儿太长，不便阅读。

原文在这儿，看的话可以从这儿开始：

源代码可从这儿下载：http://download.csdn.net/detail/tingzhiyi/9173473

效果图：

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 ADO
{
public partial class login : Form
{
public login()
{
InitializeComponent();
}
int n = 0;
private void button1_Click(object sender, EventArgs e)
{

if (tb_username.Text=="") MessageBox.Show("请输入用户名");
else if (tb_userpwd.Text=="") MessageBox.Show("请输入登录密码");
else
{
string constring = "server=Flz;database=product;Integrated Security=True;";
using (SqlConnection conn = new SqlConnection(constring))
{
string sql="select count(*) from login where username=@name and userpwd=@pwd";
SqlCommand comm = new SqlCommand(sql,conn);
comm.Parameters.AddWithValue("@name",tb_username.Text);
comm.Parameters.AddWithValue("@pwd",tb_userpwd.Text);
conn.Open();

int count=Convert.ToInt32(comm.ExecuteScalar());
#region 登录成功
if (count > 0)
{
operation f1 = new operation();
f1.Show();
this.Hide();
}
#endregion

#region 登录失败
else
{
MessageBox.Show("用户名或密码输入错误，请重新登录！");
tb_userpwd.Text = string.Empty;
tb_userpwd.Focus();
n++;
if (n>=3)
{
MessageBox.Show("密码输入次数太多，程序即将退出！");
Application.Exit();
}
}
#endregion
}
}
}
//启动程序光标跳到用户名框
private void login_Load(object sender, EventArgs e)
{
tb_username.Focus();
}

//重置用户名和密码
private void button2_Click(object sender, EventArgs e)
{
tb_username.Text = string.Empty;
tb_userpwd.Text = string.Empty;
tb_username.Focus();
}
//回车光标跳到密码框
private void tb_username_KeyPress(object sender, KeyPressEventArgs e)
{
if (e.KeyChar==13)//回车键的ASC码是13
{
tb_userpwd.Focus();
}
}
//回车登录
private void tb_userpwd_KeyPress(object sender, KeyPressEventArgs e)
{
if (e.KeyChar==13)
{
button1_Click(sender,e);
}
}

}

}