数据库 增 ，删，改， 查询

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;
namespace 登陆链接数据库
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e） //链接数据库查询
        {
            string uname = textBox1.Text;
            string upass = textBox2.Text;
            //第一步  链接数据库
            SqlConnection conn = new SqlConnection("server=.;database=yonghu;user=sa;pwd=123");
            conn.Open();
            //第二步  写执行语句
            SqlCommand cmd = conn.CreateCommand();//sqlcommand  帮助写执行语句
            cmd.CommandText = "select *from users where uname='"+uname+"'and upass='"+upass+"'";
            SqlDataReader dr = cmd.ExecuteReader();//读取执行语句  返回一个结果集
            if(dr.Read())
            {
                MessageBox.Show("登陆成功");
            }
            else
            {
                MessageBox.Show("登陆失败");
            }
            conn.Close();

        }

        private void button2_Click(object sender, EventArgs e)//链接数据库添加
        {
            string uname = textBox1.Text;
            string upass = textBox2.Text;
            //链接数据库
            SqlConnection conn = new SqlConnection("server=.;database=yonghu;user=sa;pwd=123");
            conn.Open();
            SqlCommand cmd = conn.CreateCommand();//通过conn创建sqlcommand对象
            cmd.CommandText = "insert into users values('"+uname+"','"+upass+"')";
           int count= cmd.ExecuteNonQuery();//增删改  用executenonquery  执行语句返回影响的行数
           if (count > 0)
           {
               MessageBox.Show("添加成功");
           }
           else
           {
               MessageBox.Show("添加失败");
           }
           conn.Close();
        }

        

       

        private void button3_Click(object sender, EventArgs e)//链接数据库修改
        {
            string code = textBox3.Text;
            string uname = textBox1.Text;
            string upass = textBox2.Text;
            //链接数据库
            SqlConnection conn = new SqlConnection("server=.;database=yonghu;user=sa;pwd=123");
            conn.Open();
            SqlCommand cmd = conn.CreateCommand();
            cmd.CommandText = "update users set uname='" + uname + "',upass='" + upass + "'where code=" + code;
            int count = cmd.ExecuteNonQuery();
            if (count > 0)
            {
                MessageBox.Show("修改成功");
            }
            else
            {
                MessageBox.Show("修改失败");
            }
            conn.Close();
        }

        private void button4_Click(object sender, EventArgs e)//链接数据库删除
        {
            string code = textBox3.Text;
            SqlConnection conn = new SqlConnection("server=.;database=yonghu;user=sa;pwd=123");
            conn.Open();
            SqlCommand cmd = conn.CreateCommand();
            cmd.CommandText = "delete from users where code="+code;
            int count=  cmd.ExecuteNonQuery();
            if (count > 0)
            {
                MessageBox.Show("删除成功");
            }
            else
            {
                MessageBox.Show("删除失败");
            }
            conn.Close();
        }
    }
}
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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace 增删改
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            SqlConnection conn = new SqlConnection("server=.;database=yonghu;user=sa;pwd=123");
            conn.Open();
            SqlCommand cmd = conn.CreateCommand();
            cmd.CommandText = "select *from users";
            SqlDataReader dr = cmd.ExecuteReader();
            //开始构建listview表头
            listView1.Columns.Clear();
            listView1.Columns.Add("编号");
            listView1.Columns.Add("姓名");
            listView1.Columns.Add("密码");
            //读取数据库 根据数据库内容往listview里添加行
            listView1.Items.Clear();
            while (dr.Read())
            {
                ListViewItem vi = new ListViewItem();
                vi.Text = dr["code"].ToString();
                vi.SubItems.Add(dr["uname"].ToString());
                vi.SubItems.Add(dr["upass"].ToString());
                listView1.Items.Add(vi);


            }
            conn.Close();

        }
    }
}