C# › Design Patterns in C#

How would you implement the Chain of Responsibility pattern in C# to process a request through a series of independent handlers?

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Answer

Each handler holds a reference to the NEXT handler in the chain; it either processes the request itself and stops, or passes it along to the next handler if it can't handle it — commonly implemented in ASP.NET Core's own middleware pipeline, which is essentially a real-world Chain of Responsibility implementation.

public abstract class ValidationHandler {
  protected ValidationHandler? Next;
  public ValidationHandler SetNext(ValidationHandler next) { Next = next; return next; }
  public abstract bool Handle(Order order);
}
public class CreditCheckHandler : ValidationHandler {
  public override bool Handle(Order order) =>
    CheckCredit(order) && (Next?.Handle(order) ?? true);
}

Real-world example Building a multi-step validation pipeline for an order (credit check, inventory check, fraud check) where each step can short-circuit the chain.

Common follow-ups: How does ASP.NET Core's own middleware pipeline (app.Use(...)) directly mirror this exact pattern?

Interfaces & Abstract Classes