CA1002: Do not expose generic lists

Cause

A type contains an externally visible member that is a System.Collections.Generic.List<T> type, returns a System.Collections.Generic.List<T> type, or whose signature includes a System.Collections.Generic.List<T> parameter.

Rule Description

System.Collections.Generic.List<T> is a generic collection that is designed for performance and not inheritance. System.Collections.Generic.List<T> does not contain virtual members that make it easier to change the behavior of an inherited class. The following generic collections are designed for inheritance and should be exposed instead of System.Collections.Generic.List<T>.

• System.Collections.ObjectModel.Collection<T>

• System.Collections.ObjectModel.ReadOnlyCollection<T>

• System.Collections.ObjectModel.KeyedCollection<TKey, TItem>

How to Fix Violations

To fix a violation of this rule, change the System.Collections.Generic.List<T> type to one of the generic collections that is designed for inheritance.

When to Suppress Warnings

Do not suppress a warning from this rule unless the assembly that raises this warning is not meant to be a reusable library. For example, it would be safe to suppress this warning in a performance tuned application where a performance benefit was gained from the use of generic lists.

Related Rules

CA1005: Avoid excessive parameters on generic types

CA1010: Collections should implement generic interface

CA1000: Do not declare static members on generic types

CA1006: Do not nest generic types in member signatures

CA1004: Generic methods should provide type parameter

CA1003: Use generic event handler instances

CA1007: Use generics where appropriate

See Also

Reference

Generics (C# Programming Guide)