collection and generics

A collection is simply a set of objects.

Collections can either relate to a particular kind of object or to any kind of object.

.NET contains support for both types.

For example, an ArrayList can contain objects of any kind but a List can only contain objects of type T where T needs to be specified at compile time.

List is an example of a 'generic' type where T is its type parameter. The code for a generic type is basically the same whatever the types of its parameter(s). However, the type parameters enable us to 'specialize' it for those types. This avoids having to create separate collection types for ints, strings, doubles etc. and saves a lot of time and effort.