Add products to shopping carts

To add a product in the shopping cart, you must perform the following:

1. Get the catalog manager.
   Get an instance of the CatalogManager object.
2. Get the order manager.
   Get an instance of the OrdersManager object.
3. Check whether the product is already in the cart.
   Relationship between products and carts is maintained by the Details collection of the CartOrder object. If there's a product id in the CartOrder details then the product is already added in the cart. 
4. If the product is already in the cart you need to increase the quantity.
   Use the IncreaseQuantity method of the orders manager and pass the cartDetailId and the quantity as parameters.
5. If the product is not in the cart you need to add it.
   This is achieved via the AddToCart method of the orders manager. Pass the cartOrder, product, optionsDetails and quantity as parameters.
6. Save changes.
   Save the changes to the orders manager.

Here is the full sample: