NewUser.aspx.cs

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




namespace TestGrounds
{
    public partial class NewUser : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void btnRegisterUser_Click(object sender, EventArgs e)
        {
            lblError.Text = "working...";
            bool isDuplicate = false;
            string name     = txtName.Text;
            string password = txtPassword.Text;
            string adress   = txtAdress.Text;

            SqlDataReader reader = FetchWriteData("SELECT * FROM customer");

            while (reader.Read())
            {
                if (reader["name"].ToString() == name)
                {
                    isDuplicate = true;
                    lblError.Text = "That username is already in use";
                    break;
                }

            }
            if (!isDuplicate)
            {
                SqlDataReader writer = FetchWriteData("INSERT INTO Customer(name, password, adress) VALUES('" + name + "', '" + password + "', '" + adress + "')");
                lblError.Text = "User registration complete!";
                Session["message"] = "Account Created! Please Log in";
                Response.Redirect("~/LogIn.aspx");
            }
        }

        private SqlDataReader FetchWriteData(string sql)
        {
            SqlConnection conn = new SqlConnection();

            conn.ConnectionString = WebConfigurationManager.ConnectionStrings["MinConn"].ConnectionString;

            conn.Open();

            SqlCommand cmd = new SqlCommand(sql, conn);

            SqlDataReader reader = cmd.ExecuteReader();

            return reader;
        }
    }
}