Register and login code c#

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 login_form

{

    public partial class Form1 : Form

    {

        public string connection = "Data Source=user-PC;Initial Catalog=db_test;Integrated Security=True";

        public Form1()

        {

            InitializeComponent();

        }

        private void button2_Click(object sender, EventArgs e)

        {

            SqlConnection con = new SqlConnection(connection);

            con.Open();

            SqlCommand cmd = new SqlCommand("insert into userpassword values('"+txtuser.Text+"','"+txtpass.Text+"')",con);

            if (txtpass.Text == txtconformpass.Text)

            cmd.ExecuteNonQuery();

            MessageBox.Show("insert successfully");

            con.Close();

        }

        private void button1_Click(object sender, EventArgs e)

        {

            SqlConnection con = new SqlConnection(connection);

            con.Open();

            SqlCommand cmd = new SqlCommand("select * from userpassword where username='"+textBox1.Text+"' and password='"+textBox2.Text+"' ",con);

            SqlDataReader dr = cmd.ExecuteReader();

            if (dr.HasRows)

            {

                MessageBox.Show("registered user");

            }

            else

                MessageBox.Show("please register 1st");

        }

    }

}