怎样实现winform与数据库连接

首先创建一个类,写一个专门用来查询有没有这个用户名密码的方法,

然后在按钮的事件中实例化并调用这个方法.

1.查询有没有这个类的方法

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

namespace WindowsFormsApplication2.App_Code
{
    public class UserData
    {
        SqlConnection conn = null;
        SqlCommand cmd = null;
        public UserData()
        {
            conn = new SqlConnection("server=.;database=ODA;user=sa;pwd=123;");
            cmd = conn.CreateCommand();
        }
        public bool have(string a, string b)
        {
            bool c = false;
            cmd.CommandText = "select *from Users where Username=@a and Password=@b ";
            cmd.Parameters.Clear();
            cmd.Parameters.AddWithValue("@a", a);
            cmd.Parameters.AddWithValue("@b", b);
            conn.Open();
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.HasRows)
            {
                c = true;
            }
            conn.Close();
            return c;
        }
    }
}

2.对按钮添加点击事件

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 WindowsFormsApplication2.App_Code;

namespace WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (new UserData().have(textBox1.Text, textBox2.Text))
            {
                MessageBox.Show("存在该用户");
            }
            else
            {
                MessageBox.Show("不存在该用户"); 
            }
        }
    }
}