System.Collections Namespaces

.NET Framework (current version)

The System.Collections namespaces contain types that define various standard, specialized, and generic collection objects.

Namespace Description
System.Collections The System.Collections namespace contains interfaces and classes that define various collections of objects, such as lists, queues, bit arrays, hash tables and dictionaries.
System.Collections.Concurrent The System.Collections.Concurrent namespace provides several thread-safe collection classes that should be used in place of the corresponding types in the System.Collections and System.Collections.Generic namespaces whenever multiple threads are accessing the collection concurrently. However, members accessed through one of the interfaces the current collections implement, including extension methods, are not guaranteed to be thread safe and may need to be synchronized by the caller.
System.Collections.Generic The System.Collections.Generic namespace contains interfaces and classes that define generic collections, which allow users to create strongly typed collections that provide better type safety and performance than non-generic strongly typed collections.
System.Collections.ObjectModel The System.Collections.ObjectModel namespace contains classes that can be used as collections in the object model of a reusable library. Use these classes when properties or methods return collections.
System.Collections.Specialized The System.Collections.Specialized namespace contains specialized and strongly-typed collections; for example, a linked list dictionary, a bit vector, and collections that contain only strings.