数据库简单增删改查

namespace 数据库增删改查
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e) //登陆(查询)
        {
            string user = textBox2.Text;
            string password = textBox3.Text;

            SqlConnection coon = new SqlConnection("server=.;database=enter;user=sa;pwd=123"); //连接数据库
            coon.Open();//打开数据库
            SqlCommand cmd = coon.CreateCommand();//执行查询语句
            cmd.CommandText = "select * from enters where username='"+user+"' and userpass='"+password+"'"; //进行匹配
            SqlDataReader dr = cmd.ExecuteReader();//执行查询，将结果反馈给dr
            if (dr.Read())
            {
                MessageBox.Show("登陆成功");
            }
            else
            {
                MessageBox.Show("登陆失败");
            }
            coon.Close();

        }

        private void button3_Click(object sender, EventArgs e) //添加
        {
            string user = textBox2.Text;
            string password = textBox3.Text;
            SqlConnection coon = new SqlConnection("server=.;database=enter;user=sa;pwd=123");
            coon.Open();
            SqlCommand cmd = coon.CreateCommand();
            cmd.CommandText = "insert into enters values('"+user+"','"+password+"')";
            int count = cmd.ExecuteNonQuery();//增删改都用这个
            if(count>0)
            {
                MessageBox.Show("添加成功");
            }
            coon.Close();
        }

        private void button2_Click(object sender, EventArgs e) //修改
        {
            string code = textBox1.Text;
            string user = textBox2.Text;
            string password = textBox3.Text;
            SqlConnection coon = new SqlConnection("server=.;database=enter;user=sa;pwd=123");
            coon.Open();
            SqlCommand cmd = coon.CreateCommand();
            cmd.CommandText = "update enters set username='"+user+"' , userpass='"+password+"' where code="+code;
            int count = cmd.ExecuteNonQuery();
            if(count>0)
            {
                MessageBox.Show("修改成功");
            }
            else
            {
                MessageBox.Show("修改失败！");
            }
            coon.Close();
        }

        private void button4_Click(object sender, EventArgs e) //删除
        {
            string code = textBox1.Text;
            SqlConnection coon = new SqlConnection("server=.;database=enter;user=sa;pwd=123");
            coon.Open();
            SqlCommand cmd = coon.CreateCommand();
            cmd.CommandText = "delete from enters where code="+code;
            cmd.ExecuteNonQuery();
            coon.Close();
        }
    }
}