The System.Collections namespace contains useful classes for storing collections of objects. All collections implement the interface, which provides basic functionality for iterating through the elements of a collection. Collections that support index-based access into their elements and the ability to add and remove elements, such as the , implement the interface. Collections that provide a key/value mapping, such as the , implement the interface.

The namespace contains interfaces and classes that define various collections of objects, such as lists, queues, bit arrays, hash tables and dictionaries.