what is the business logic code for this three tier architecture application?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using BLL;
using DAL;

namespace _3_tiersample
{
    public partial class RegistrationForm : System.Web.UI.Page
    {
        classBLL Objbal = new classBLL();
        protected void Page_Load(object sender, EventArgs e)
        {
         
        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            try
            {
                string Output = string.Empty;
                classBLL Objbalregistration = new classBLL();
                Objbalregistration.Name = TextBox1.Text;
                Objbalregistration.Roll_Number = Convert.ToInt32(TextBox2.Text);
                Objbalregistration.Email_Id = TextBox3.Text;
                Objbalregistration.Mobile_Number = TextBox4.Text;
                Objbalregistration.InsertUserDetails(Objbal);
                Console.WriteLine("Data Inserted");
            }
            catch(Exception Ex)
            {
                Console.WriteLine(Ex);
            }
        }

    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using DAL;


namespace BLL
{
    public class classBLL
    {
        private string _Name;
        private int _Roll_Number;
        private string _Email_Id;
        public string _Mobile_Number;


        public string Name
        {
            set { _Name = value; }
            get { return _Name; }
        }
        public int Roll_Number
        {
            set { _Roll_Number = value; }
            get { return _Roll_Number; }
        }
        public string Email_Id
        {
            set { _Email_Id = value; }
            get { return _Email_Id; }
        }
        public string Mobile_Number
        {
            set { _Mobile_Number = value; }
            get { return _Mobile_Number; }
        }

    }
}

using System.Text;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using BLL;

namespace DAL
{
    public class classDAL
    {
        string connection = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
     
        public void InsertUserDetails(classBLL Objbal)
      {
          SqlConnection con = new SqlConnection(connection);
          SqlCommand cmd = new SqlCommand("sp_InsertEmpdetails", con);
          cmd.CommandType = CommandType.StoredProcedure;
          con.Open();
          try
          {
              cmd.Parameters.AddWithValue("@Name", Objbal.Name);
              cmd.Parameters.AddWithValue("@Roll_Number", Objbal.Roll_Number);
              cmd.Parameters.AddWithValue("@Email_Id", Objbal.Email_Id);
              cmd.Parameters.AddWithValue("@Mobile_Number", Objbal.Mobile_Number);
              Console.WriteLine( "data saved");
          }
          catch (Exception Ex)
          {
              Console.WriteLine(Ex);
          }
          finally
          {
              con.Dispose();
          }

      }
       
    }  
}