References

Reference materials for deeper learning.

Official Documentation

Functorium

• GitHub: https://github.com/hhko/Functorium
• Specification Types: Src/Functorium/Domains/Specifications/

.NET Expression Trees

• Official Docs: https://learn.microsoft.com/en-us/dotnet/csharp/advanced-topics/expression-trees/
• Expression Trees Advanced: https://learn.microsoft.com/en-us/dotnet/csharp/advanced-topics/expression-trees/expression-trees-building

ArchUnitNET

• GitHub: https://github.com/TNG/ArchUnitNET
• NuGet: https://www.nuget.org/packages/TngTech.ArchUnitNET.xUnit

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References

Domain-Driven Design

• Title: Domain-Driven Design: Tackling Complexity in the Heart of Software
• Author: Eric Evans
• Publisher: Addison-Wesley, 2003
• Key Content: Foundational definition of the Specification pattern, Repository pattern

Implementing Domain-Driven Design

• Title: Implementing Domain-Driven Design
• Author: Vaughn Vernon
• Publisher: Addison-Wesley, 2013
• Key Content: Practical DDD implementation patterns, Specification usage examples

Patterns of Enterprise Application Architecture

• Title: Patterns of Enterprise Application Architecture
• Author: Martin Fowler
• Publisher: Addison-Wesley, 2002
• Key Content: Systematic definition of Specification pattern and Repository pattern

Functional Programming in C#

• Title: Functional Programming in C#: How to write better C# code
• Author: Enrico Buonanno
• Publisher: Manning, 2022 (2nd Edition)
• Key Content: Expression Trees, functional composition patterns

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Online Resources

Blogs & Articles

Specification Pattern

• https://www.martinfowler.com/apsupp/spec.pdf
• Original Specification pattern paper by Eric Evans and Martin Fowler

Specification Pattern in DDD

• https://enterprisecraftsmanship.com/posts/specification-pattern-always-valid-domain-model/
• Vladimir Khorikov on the Specification pattern and always-valid domain models

Expression Trees in C#

• https://learn.microsoft.com/en-us/dotnet/csharp/advanced-topics/expression-trees/
• Official .NET Expression Tree guide

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Related Libraries

Specification Pattern

Library	Description	NuGet
Functorium	Specification framework used in this tutorial	✅
Ardalis.Specification	Specification library by Steve Smith	✅

DDD & Clean Architecture

Library	Description	NuGet
MediatR	CQRS/Mediator pattern	✅
FluentValidation	Validation library	✅
LanguageExt.Core	Functional programming types	✅

ORM

Library	Description	NuGet
Microsoft.EntityFrameworkCore	EF Core ORM	✅
Microsoft.EntityFrameworkCore.InMemory	InMemory for testing	✅

Testing

Library	Description	NuGet
ArchUnitNET	Architecture testing	✅
Shouldly	Assertion library	✅
xUnit	Testing framework	✅
NSubstitute	Mocking library	✅

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Functorium Project Reference

Source Code Location

Src/Functorium/Domains/Specifications/
├── Specification.cs                       # Abstract base class
├── IExpressionSpec.cs                     # Expression interface
├── ExpressionSpecification.cs             # Expression Tree support
├── AllSpecification.cs                    # Identity element (internal sealed)
├── AndSpecification.cs                    # AND composition (internal sealed)
├── OrSpecification.cs                     # OR composition (internal sealed)
├── NotSpecification.cs                    # NOT negation (internal sealed)
└── Expressions/
    ├── SpecificationExpressionResolver.cs # Expression synthesis utility
    └── PropertyMap.cs                     # Entity->Model conversion

Tutorial Projects

Docs.Site/src/content/docs/tutorials/specification-pattern/
├── Part1-Specification-Basics/            # Basics (4 chapters)
├── Part2-Expression-Specification/        # Expression (4 chapters)
├── Part3-Repository-Integration/          # Repository Integration (4 chapters)
├── Part4-Real-World-Patterns/             # Real-World Patterns (4 chapters)
└── Part5-Domain-Examples/                 # Domain Examples (2 chapters)

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Recommended Learning Path

Beginner (Pattern Introduction)

1. Specification chapter in Eric Evans’ DDD book
2. This tutorial Part 1 (Chapters 1-4)
3. Read the Functorium Specification source code

Intermediate (Practical Application)

1. .NET Expression Trees official documentation
2. This tutorial Parts 2-3
3. Comparative analysis with Ardalis.Specification

Advanced (Architecture Design)

1. “Implementing Domain-Driven Design” book
2. This tutorial Parts 4-5
3. Writing architecture tests with ArchUnitNET

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This tutorial was written based on the actual development experience of the Functorium project’s Specification framework.