ChainOfResponsibility

Chain of Responsibility Pattern

Intent

Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it.

Problem

You need to process a request through multiple handlers, but you don't want to hard-code which handler processes which request.

Solution

The Chain of Responsibility pattern passes requests along a chain of handlers. Each handler decides either to process the request or to pass it to the next handler in the chain.

When to Use

• More than one object may handle a request, and the handler isn't known in advance
• You want to issue a request to one of several objects without specifying the receiver explicitly
• The set of objects that can handle a request should be specified dynamically

C# Implementation

See the Program.cs file for a support ticket escalation system demonstrating the chain of responsibility.

Pros

• Can control the order of request handling
• Single Responsibility Principle - decouple classes that invoke and perform operations
• Open/Closed Principle - introduce new handlers without breaking existing code

Cons

• Some requests may end up unhandled
• Can be hard to observe runtime characteristics of the chain