C#

class MainForm : Form
{
    private string chosenPizza = "Pepperoni";
    private bool cheesy = true;

    private void buttonChooseNewPizza_Click(object sender, EventArgs e)
    {
        PizzaOrderForm orderForm = new PizzaOrderForm();
        orderForm.PizzaType = chosenPizza;
        orderForm.Cheesy = cheesy;
        DialogResult answer = orderForm.ShowDialog(this);
        if (answer == DialogResult.OK)
        {
            chosenPizza = orderForm.PizzaType;
            cheesy = orderForm.Cheesy;
            labelOrderStatus.Text = "Your " + chosenPizza + " pizza with" +
                                    (cheesy ? "" : "out") + 
                                    " cheese is coming right up!";
        }
    }
}

partial class PizzaOrderForm : Form
{
  public PizzaOrderForm()
  {
     InitializeComponent();
  }

  private string pizzaType;
  public string PizzaType
  {
     get
     {
        return pizzaType;
     }
     set
     {
        switch (value.ToLower())
        {
           case "pepperoni":
           case "hawaiian":
           case "vegetarian":
              pizzaType = value;
              break;
           default:
              throw new ArgumentOutOfRangeException(string.Format("Sorry, {0} pizza is not on the menu.", value ));
        }
     }
  }
  private bool cheesy = true;
  public bool Cheesy
  {
     get
     {
        return cheesy;
     }
     set
     {
        cheesy = value;
     }
  }

  private void PizzaOrderForm_Load(object sender, EventArgs e)
  {
     textBoxPizza.Text = PizzaType;
     checkBoxCheese.Checked = Cheesy;
  }

  private void buttonOK_Click(object sender, EventArgs e)
  {
     PizzaType = textBoxPizza.Text;
     Cheesy = checkBoxCheese.Checked;
  }
}

bool isNumber = System.Text.RegularExpressions.Regex.IsMatch(stringValue, "[0-9]");