Software 1 - Class Exercise 5

Goals

• Use an extension method to add functionality to a class you wouldn't normally have access to.

Instructions

We're going to extend List to check for in stock items. This is a check that we would potentially do a lot in the future of our program. So adding a method to do this will make the code more readable and easier to maintain.

1. Create a new static class. Call it ListExtensions.
2. In this class we're going to create a static method. This one will be kind of complicated, so here's the method signature: public static List<T> InStock<T>(this List<T> list) where T: Product.
3. Your mentors should have explained a little bit about generics. They're not critical to understanding extension methods, but hopefully it will take some of the mystery out of how the method is working. You'll learn much more about generics in the next course.
4. In the method body, return the "in stock" code we wrote last time. Since this method is returning a list, remember to add the ToList at the end.
5. We can now use this new method in our ProductLogic class. Go replace the "in stock" logic with this new method.
6. Add a new method (don't forget the interface) called GetTotalPriceOfInventory. It will return a decimal. Use your new InStock method, the Select method, and the Sum method to get your result.
7. Add a new UI option for the new method.
8. Now just test to make sure it works correctly.