SOLID & Design Patterns Interview Question #7

What are common signs of an LSP violation?

SOLID Principles, Design Fundamentals, Repository, Factory, Strategy & Decorator Junior Beginner

Quick Interview Answer

A subtype that throws NotSupportedException for an operation promised by the base abstraction is a common warning sign. Another is when callers must check the concrete subtype before safely using a base reference.

Detailed Explanation

These symptoms often indicate that the inheritance hierarchy models the domain incorrectly and should be redesigned using smaller abstractions or composition.

Code Example

public abstract class Bird
{
    public abstract void Fly();
}

public class Penguin : Bird
{
    public override void Fly()
        => throw new NotSupportedException();
}