/// <summary>
        /// Adds the ingredients(Factory).
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void AddIngredientBtn_Click(object sender, RoutedEventArgs e)
        {
            this.pizza.AddIngredient(IngredientFactory.CreateIngredient(IngredientList.ThinCrust));
            this.pizza.AddIngredient(IngredientFactory.CreateIngredient(IngredientList.Marinara));
            this.pizza.AddIngredient(IngredientFactory.CreateIngredient(IngredientList.Mozzarella));
            this.pizza.AddIngredient(IngredientFactory.CreateIngredient(IngredientList.Pepperoni));

            // This should throw exceptions
            // this.pizza.AddIngredient(IngredientFactory.CreateIngredient(IngredientList.ThickCrust));
            // this.pizza.AddIngredient(IngredientFactory.CreateIngredient(IngredientList.BBQ));

            this.PizzaLbl.Text    = this.pizza.ToString();
            this.PriceLbl.Content = string.Format("Price: {0:C}", this.pizza.CalculatePrice());
        }