/// <summary>
 /// Adds items to the cart
 /// </summary>
 /// <param name="obj"></param>
 private void AddToCart(object obj)
 {
     if (obj != null)
     {
         ItemsSelected += obj.ToString();
     }
     // Calculate the total amount when added to the cart
     if (!string.IsNullOrWhiteSpace(ItemsSelected))
     {
         if (_itemService != null)
         {
             TotalAmount = _itemService.CalculateTotalAmount(ItemsSelected);
         }
     }
     PrepareItemsBillInfo();
 }