Register.aspx.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;

public partial class Register : System.Web.UI.Page
{
    protected void RegisterButt_Click(object sender, EventArgs e)
    {
        string connection = @"Data Source=.\SQLEXPRESS;AttachDbFilename=C:\Users\Gal\Desktop\WebApplication2\WebApplication2\App_Data\MyDB.mdf;Integrated Security=True;User Instance=True";
        SqlConnection CS = new SqlConnection(connection);
        CS.Open();
        SqlCommand userNameCheck = new SqlCommand(String.Format("select * from users where username = '{0}'", UserName.Text), CS);
        SqlDataReader reader = userNameCheck.ExecuteReader();
        if (!reader.HasRows)
        {
            reader.Close();
            SqlCommand EmailCheck = new SqlCommand(String.Format("select * from users where email = '{0}'", email.Text), CS);
            SqlDataReader Reader2 = EmailCheck.ExecuteReader();
            if (!Reader2.HasRows)
            {
                Reader2.Close();
                SqlCommand command = new SqlCommand(String.Format("insert into users (username, password, email) values ('{0}','{1}','{2}')", UserName.Text, Password.Text, email.Text), CS);
                command.ExecuteNonQuery();
                CS.Close();
            }
            else
            {
                Response.Write("<script type='text/javascript'>alert('Email is already registered')</script>");
            }
        }
        else
        {
            Response.Write("<script type='text/javascript'>alert('Username is already taken')</script>");
        }
    }
}