Отладка однопоточного приложения в Visual Studio 2010

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Collections;
namespace WindowsDebugApplication
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private double c =0;
        private void Plus(double a,double b)
        {
           c = a + b;
        }
        private void Minus(double a, double b)
        {
            c = a - b;
        }
        private void Multiply(double a, double b)
        {
            c = a * b;
        }
        private void Split(double a, double b)
        {
            c = a / b;
        }
        private void ResultButton_Click(object sender, EventArgs e)
        {
           string symbol =(string) SymbolcomboBox.SelectedItem;
           ArrayList arraysymbol = new ArrayList();
           foreach (var s in SymbolcomboBox.Items)
           {
               arraysymbol.Add(s);
           }
           double var1 =Convert.ToDouble(FirstVariable.Text);
           double var2 = Convert.ToDouble(SecondVariable.Text);
           switch (symbol)
           {
               case "+": Plus(var1, var1); break;
               case "-": Minus(var1, var1); break;
               case "*": Multiply(var1, var1); break;
               case "/": Split(var1, var1); break;
           }
           MessageBox.Show("Результат: " + c);
           MessageBox.Show("Количество символов в коллекции: "+ arraysymbol.Count);
        }
    }
}