This course introduces collection classes and describes how you can use them with greater flexibility than a simple array. Classes that act on other types are often not type-safe and must be cast back to their original type before they can be used. An understanding of generics and the use of generic classes to maintain type integrity is important for avoiding issues associated with a lack of type safety. The course also describes how to build and enumerate custom collection classes, which enable you to store collections of objects that you would be unable to store if you were to use the collection classes that are provided in the Microsoft® .NET Framework.