gof-design-patterns

Imported from SerhiiVoznyi/DesignPatterns (SKILL.md). Install upstream with npx skills add SerhiiVoznyi/DesignPatterns. Copyright stays with the author.

GoF with Gof.DesignPatterns

Metadata

Load this skill when choosing or implementing one of the twelve shipped patterns. Skip it for unrelated C# work or unpublished GoF patterns (Observer, Decorator, and similar) unless the task is to extend the library.

Use when

• Writing or reviewing C# that should share these pattern contracts.
• Choosing among the 12 patterns this package actually ships.

Not when

• The user did not ask to extend the library: do not add missing GoF types (Observer, Decorator, Facade, Proxy, …) to this repo.
• A simpler constructor, function, or DI registration already solves the problem.

Library facts

• Package: Gof.DesignPatterns. Interfaces plus a few bases — consumers implement domain types.
• Namespaces: DesignPatterns, DesignPatterns.Implementation, DesignPatterns.Concurrent (Task / *Async).
• Snippets and intent text: README.md. Read it before inventing members.

Method

1. Name the problem: creation, structure, or behavior.
2. Pick one pattern from the map below.
3. Implement the matching interface (or inherit the listed base). Inject implementations via constructors in app code.
4. If the work is already async, use DesignPatterns.Concurrent counterparts, not .Result / .Wait().

Pattern to type map

Concurrent types live in DesignPatterns.Concurrent (and DesignPatterns.Concurrent.Implementation for CoR). Same pattern names; async method names (CreateAsync, HandleAsync, ExecuteAsync, …).

Caveats

• Abstract Factory: generic interfaces model one product role. A GoF product family needs an explicit multi-method interface you define.
• Singleton: GetInstance() is an instance method. where TThis : new() does not forbid new TThis(). Prefer GetInstance() as the access point. Do not use Singleton for services the host already manages with DI unless there is a clear reason.
• Chain of Responsibility: AddNextHandler registers the next link and returns that next handler. RegisterNext replaces the current successor.
• Do not call members that are not on these types. Confirm against source or the README.

Failure modes

• Inventing APIs or README sample types (Company, Widget) as if they shipped in the package.
• Treating this library as a full GoF catalog or as finished pattern implementations.
• Using SingletonBase when a scoped/singleton DI registration is enough.