Prerequisites and Setup

Please verify the following items before starting the tutorial.

Required Tools

Tool	Version	Purpose
.NET SDK	10.0 or higher	Build and run
VS Code	Latest	Code editing
C# Dev Kit	Latest	C# development support

Prerequisite Knowledge

You should be familiar with the following concepts to study this tutorial:

Concept	Level	Description
C# Generics	Basic	Basic generic syntax like `List<T>`, `where T : class`
Interfaces	Basic	Interface definition, implementation, polymorphism
Record types	Basic	`record class`, sealed record, positional record
Mediator pattern	Optional	Needed from Part 2 onward (not required for Part 1)

Project Build

# Clone the repository
git clone https://github.com/hhko/Functorium.git
cd Functorium

# Build the tutorial
dotnet build Docs.Site/src/content/docs/tutorials/usecase-pipeline/usecase-pipeline.slnx

# Run tutorial tests
dotnet test --solution Docs.Site/src/content/docs/tutorials/usecase-pipeline/usecase-pipeline.slnx

# Build the entire solution
dotnet build Functorium.slnx

Project Types

The projects in this tutorial are divided into two types:

Type	Part	References	Description
Standalone	Part 1, 2 (Sections 2-3), 3	LanguageExt.Core only	For concept learning, independently runnable
Functorium Reference	Part 2 (Section 1), 4, 5	Functorium.csproj	Practical application, uses Pipeline/Usecase

Standalone Projects

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="LanguageExt.Core" />
  </ItemGroup>
</Project>

Functorium Reference Projects

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
  </PropertyGroup>
  <ItemGroup>
    <ProjectReference Include="..\..\..\..\..\Src\Functorium\Functorium.csproj" />
  </ItemGroup>
</Project>

Recommended Study Order

It is recommended to study Parts 1-3 in order. Parts 4-5 can be studied freely after completing Part 3.

FAQ

Q1: Can Part 1 be studied without Mediator pattern knowledge?

A: Yes. Part 1 covers only C# generic variance (covariance/contravariance/invariance), so Mediator pattern knowledge is not needed. IPipelineBehavior first appears in Part 2, so understanding the basics of the Mediator pattern by then is sufficient.

Q2: What is the difference between Standalone and Functorium Reference projects?

A: Standalone projects reference only LanguageExt.Core and are independently runnable for concept learning. Functorium Reference projects reference Functorium.csproj and are used for practical Pipeline and Usecase implementation. Parts 1-3 primarily use Standalone, while Parts 4-5 use Functorium Reference projects.

Q3: Can I follow the tutorial with a .NET SDK version earlier than 10.0?

A: This tutorial uses C# 11’s static abstract members and modern record syntax. static abstract is supported from .NET 7 onward, but since the project build settings target .NET 10, .NET SDK 10.0 or higher is recommended.

The following section examines the overall structure of Mediator Pipelines and the capabilities each Pipeline requires from the response type.

→ Section 0.3: Usecase Pipeline Architecture Overview