The System.Collections.Generic namespace contains several generic collection classes based on generics and it is recommended that we should use these collection classes in lieu of the earlier non-generic ones for better performance of our applications.

According to MSDN, "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."

Note that the System.Collections.Generic.ICollection<T> interface is the base interface for all the classes in the System.Collections.Generic namespace.