Exception Handling in 3-Tier Architecture

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using Common.Helpers.DataAccess;
using Common.Helpers.ExceptionHandling;
using System.Data.SqlClient;

namespace HelpersTestWeb
{
   public partial class _Default : System.Web.UI.Page
   {

      protected void Page_Load(object sender, EventArgs e)
      {
         if (!IsPostBack)
         {
            GridView1.Visible = false;
            TextBox1.Visible = false;
         }
      }

      protected void btnScenario1_Click(object sender, EventArgs e)
      {
         try
         {
            DataTable dt = MyClass.GetCustomersList();
            GridView1.DataSource = dt;
            GridView1.DataBind();
            GridView1.Visible = true;
         }
         catch (Exception ex)
         {
            TextBox1.Visible = true;
            TextBox1.Text = ex.Message.ToString();
         }
      }

      protected void btnScenario2_Click(object sender, EventArgs e)
      {
         try
         {
            object ret = MyClass.InsertCustomer("ABC", "ABC INC");
         }
         catch (Exception ex)
         {
            TextBox1.Visible = true;
            TextBox1.Text = ex.Message.ToString();
         }
      }

      protected void btnScenario3_Click(object sender, EventArgs e)
      {
         try
         {
            DataTable dt = MyClass.GetCustomerData("");
            GridView1.DataSource = dt;
            GridView1.DataBind();
            GridView1.Visible = true;
         }
         catch (Exception ex)
         {
            TextBox1.Visible = true;
            TextBox1.Text = ex.Message.ToString();
         }
      }
      protected void btnScenario4_Click(object sender, EventArgs e)
      {
         try
         {
            int result = MyClass.DoSomeCalculation(10, 0);
            TextBox1.Visible = true;
            TextBox1.Text = "Calculation performed successfully. Result is " + result.ToString();
         }
         catch (Exception ex)
         {
            TextBox1.Visible = true;
            TextBox1.Text = ex.Message.ToString();
         }
      }

      protected void btnScenario5_Click(object sender, EventArgs e)
      {
         try
         {
            MyClass.SaveInvoice("ABC", 1200);
            TextBox1.Visible = true;
            TextBox1.Text = "Invoice saved successfully";
         }
         catch (Exception ex)
         {
            TextBox1.Visible = true;
            TextBox1.Text = ex.Message.ToString();
         }
      }
      protected void btnScenario6_Click(object sender, EventArgs e)
      {
         try
         {
            //intentially raising Divide by Zero exception
            int a, b, c;
            a = 20;
            b = 0;
            c = a / b;
            TextBox1.Visible = true;
            TextBox1.Text = "Divided Successfully. Result is " + c.ToString();
         }
         catch (Exception ex)
         {
            bool rethrow = false;
            rethrow = UserInterfaceExceptionHandler.HandleExcetion(ref ex);
            TextBox1.Visible = true;
            TextBox1.Text = ex.Message.ToString();
         }
      }
   }
}