Why Should You Avoid Inheriting from List?

Why You Should Generally Avoid Inheriting from List<T>

While seemingly convenient for creating custom collections, inheriting from List<T> presents several significant drawbacks.

Performance Concerns:

List<T> is highly optimized for performance. Inheritance can inadvertently disrupt these optimizations, leading to slower execution.

API Design Issues:

Inheriting List<T>'s public methods exposes implementation details, reducing flexibility for future modifications, especially when creating public APIs.

Rigidity and Limited Extensibility:

List<T>'s general-purpose nature may clash with a custom collection's specific requirements. Inheritance can create an inflexible design unable to accommodate unique features or behaviors.

Better Alternatives:

Microsoft suggests Collection<T> as a more suitable base class, though it provides a less feature-rich starting point.

Composition over Inheritance:

A superior approach is often composition: encapsulate a List<T> instance within your custom class. This extends functionality without compromising the original List<T> performance or behavior.

Modeling Custom Structures Effectively:

Instead of viewing a custom structure as a "decorated list," treat it as a distinct entity. Define its core properties and behaviors, then model them directly.

Acceptable Scenarios for Inheritance:

There are limited situations where inheriting from List<T> is justifiable:

• Extending existing functionality: Adding custom sorting methods, for example.
• Domain-specific collections: Where features can be reasonably added without impacting List<T>'s performance or design integrity. Careful consideration is crucial in these cases.

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