Form1.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 _001
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string sql = "select count(*) from tbusers where loginid=@loginid and loginpwd=@loginpwd";
            SqlParameter[] pms = new SqlParameter[]{
            new SqlParameter("@loginid",SqlDbType.VarChar,50){Value=textBox1.Text.Trim()},
            new SqlParameter("@loginpwd",SqlDbType.VarChar,50){Value=textBox2.Text.Trim()}
            };
            int i=(int)SqlHelper.ExecuteScalar(sql,pms);
            if(i>0)
            {
            this.Text="成功";
            }
            else
            {
            this.Text="失败";
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            //声明集合
            List<tbusers> list= new List<tbusers>();
            string sql="select loginid,loginpwd from tbusers";
            using (SqlDataReader reader = SqlHelper.ExecuteReader(sql))
            {
                if (reader.HasRows)
                {
                    while (reader.Read())
                    {
                        //添加到数据模型
                        tbusers model = new tbusers();
                        model.loginid = reader.GetString(0);
                        model.loginpwd = reader.GetString(1);

                        //把数据添加到集合里
                        list.Add(model);
                    }
                }
            }
            //将集合的数据绑定到dataGridView控件
            dataGridView1.DataSource = list;
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }
    }
}