Vb.net 2010 Calculator Program

Hello I am doing a calculator program in VB.net 2010.  I am almost done with the program but there is just one problem.  The calculator works correctly with entering a number, clicking the operation, and entering another number however when I click the equals sign it doesn't give the answer. I've looked over the code and can't seem to find the flaw.  Could somebody please help.

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

namespace User_Control_Assignment
{
    public partial class User_Control : System.Web.UI.UserControl
    {
        int addition1,subtraction1,division1,multiplication1,result;
        int choice;
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void Btn1_Click(object sender, EventArgs e)
        {
            
            TextBoxAnswer.Text = TextBoxAnswer.Text + Btn1.Text;
        }

        protected void Btb2_Click(object sender, EventArgs e)
        {
            TextBoxAnswer.Text = TextBoxAnswer.Text + Btb2.Text;
        }

        protected void Btn3_Click(object sender, EventArgs e)
        {
            TextBoxAnswer.Text = TextBoxAnswer.Text + Btn3.Text;
        }

        protected void Btn4_Click(object sender, EventArgs e)
        {
            TextBoxAnswer.Text = TextBoxAnswer.Text + Btn4.Text;
        }

        protected void Btn5_Click(object sender, EventArgs e)
        {
            TextBoxAnswer.Text = TextBoxAnswer.Text + Btn5.Text;
        }

        protected void Btn6_Click(object sender, EventArgs e)
        {
            TextBoxAnswer.Text = TextBoxAnswer.Text + Btn6.Text;
        }

        protected void Btn7_Click(object sender, EventArgs e)
        {
            TextBoxAnswer.Text = TextBoxAnswer.Text + Btn7.Text;
        }

        protected void Btn8_Click(object sender, EventArgs e)
        {
            TextBoxAnswer.Text = TextBoxAnswer.Text + Btn8.Text;
        }

        protected void Btn9_Click(object sender, EventArgs e)
        {
            TextBoxAnswer.Text = TextBoxAnswer.Text + Btn9.Text;
        }
        protected void Btn0_Click(object sender, EventArgs e)
        {
            TextBoxAnswer.Text = TextBoxAnswer.Text + Btn0.Text;
        }

        protected void BtnMult_Click(object sender, EventArgs e)
        {
            multiplication1 = int.Parse(TextBoxAnswer.Text);
            TextBoxAnswer.Text = "";
            choice = 4;
        }

        

        protected void BtnDiv_Click(object sender, EventArgs e)
        {
            division1 = int.Parse(TextBoxAnswer.Text);
            TextBoxAnswer.Text = "";
            choice = 3;

        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            addition1 = int.Parse(TextBoxAnswer.Text);
            TextBoxAnswer.Text = "";
            choice = 1;

        }

        protected void BtnSub_Click(object sender, EventArgs e)
        {
            subtraction1 = int.Parse(TextBoxAnswer.Text);
            TextBoxAnswer.Text = "";
            choice = 2;
        }

        protected void BtnEquals_Click(object sender, EventArgs e)
        {
            switch (choice)
            {
                case 1:
                    result = addition1 + int.Parse(TextBoxAnswer.Text);
                    TextBoxAnswer.Text = result.ToString();
                    break;
                case 2:
                    result = subtraction1 + int.Parse(TextBoxAnswer.Text);
                    TextBoxAnswer.Text = result.ToString();
                    break;
                case 3:
                    result = division1 + int.Parse(TextBoxAnswer.Text);
                    TextBoxAnswer.Text = result.ToString();
                    break;
                case 4:
                    result = multiplication1 + int.Parse(TextBoxAnswer.Text);
                    TextBoxAnswer.Text = result.ToString();
                    break;
            }
        }
        protected void BtnClr_Click(object sender, EventArgs e)
        {
            TextBoxAnswer.Text = "";
        }

       
        
    }
}