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

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            using (SqlConnection con = new SqlConnection(
@"Data Source=.\SQLEXPRESS;AttachDBFilename=|DataDirectory|\mydb.mdf;Integrated Security=True;User Instance=True"))
            {
                con.Open();
                using (SqlCommand cmd = con.CreateCommand())
                {
                     = "Select * from Table1 where username=@un";
                    cmd.Parameters.Add(new SqlParameter("un", textBox1.Text));
                    using (SqlDataReader reader = cmd.ExecuteReader())
                    {
                        if (reader.Read())
                        {
                            string pw = reader.GetString(reader.GetOrdinal("password"));
                            if (pw == textBox2.Text)
                            {
                                MessageBox.Show("登陆成功！");
                            }
                            else
                            {
                                MessageBox.Show("登录失败！");
                            }
                        }
                        else
                        {
                            MessageBox.Show("用户名不存在！");
                        }
                    }
                }
            }




        }

        private void label2_Click(object sender, EventArgs e)
        {

        }

        private void button2_Click(object sender, EventArgs e)
        {
            using (SqlConnection con = new SqlConnection(
@"Data Source=.\SQLEXPRESS;AttachDBFilename=|DataDirectory|\mydb.mdf;Integrated Security=True;User Instance=True"))
            {
                con.Open();
      
                  
                   string upd = "Insert into Table1(username,password) values('textBox1.Text' ,'textBox2.Text')";
                 
                   SqlCommand mycmd = new SqlCommand(upd,con);
                    MessageBox.Show("注册成功！！");
               
            }
        }
    }
}


说明：快速注册的功能是向数据库插入数据，但是调试之后去数据库查看，并没有插入新数据。编译没有出错~