Functional.Types

Functional primitives and extensions for C#.

Functional.Types (NuGet: Functional.Types) is a lightweight library of functional primitives and helpers for .NET:

• Option<T> — optional values and combinators.
• Result<T, E> — explicit success/failure flow.
• Unit — a single value type representing absence of data.
• Error and Validator — small validation helpers.

In addition to the core library, this repository contains a separate package for Entity Framework Core integration: Functional.Types.EntityFrameworkCore.

Contents

• Functional.Types
  • Contents
  • Overview
  • Packages
  • Installation
  • Quick examples
  • Migration notes
  • Build & tests
  • Versioning & releases
  • Contributing
  • Licence

Overview

Functional.Types aims to provide a small, well-tested set of types and extensions to make functional-style code straightforward in C#, while keeping the core package free of heavier dependencies. Integrations (for example EF Core) are distributed as optional, separate packages to avoid unnecessary transitive dependencies.

Principles:

• Small dependency-free core.
• Composable primitives with clear semantics.
• Opt-in integration packages.

Packages

• Functional.Types — core primitives and helpers.
• Functional.Types.EntityFrameworkCore — EF Core IQueryable extensions and async/sync helpers (for example FirstOrNoneAsync, SingleOrNoneAsync), which depends on Functional.Types.

Package IDs published to NuGet follow the project names under /src.

Installation

Install the core package using dotnet:

dotnet add package Functional.Types

For EF Core integration:

dotnet add package Functional.Types.EntityFrameworkCore

Both packages target .NET 10 (net10.0).

Quick examples

Option handling:

using Functional.Types;

Option<int> maybe = Option.Some(3);

int doubled = maybe.Match(
  some: v => v * 2,
  none: () => 0
);

Result usage:

using Functional.Types;

Result<int, string> r = Result.Ok<int, string>(42);

r.Match(
  ok: v => Console.WriteLine($"Value: {v}"),
  err: e => Console.WriteLine($"Error: {e}")
);

EF Core example (async):

using Functional.Types.EntityFrameworkCore.Option.Extensions.IQueryable;

var maybeUser = await dbContext.Users.Where(u => u.Id == id).FirstOrNoneAsync();

Migration notes

• EF Core extensions were extracted from the core package. If you previously relied on EF extensions being present in the main package, add a dependency on Functional.Types.EntityFrameworkCore.

Build & tests

Requirements: .NET 10 SDK

From the repository root:

dotnet build
dotnet test

The repository includes GitHub Actions workflows for CI and automated publishing.

Versioning & releases

This project uses GitVersion (ContinuousDeployment) along with a calendar-tag release process (YYYY.MM.PATCH). The nuget.yml workflow generates release notes from Conventional Commit messages when an annotated tag is pushed.

To create packages locally:

dotnet pack src/Functional/Functional.csproj -c Release
dotnet pack src/Functional.EntityFrameworkCore/Functional.EntityFrameworkCore.csproj -c Release

To publish to NuGet, set NUGET_API_KEY in your CI environment and push an annotated tag to trigger the workflow.

Contributing

Contributions are welcome. Quick guidelines:

• Use Conventional Commits for commit messages.
• Add tests for new behaviour.
• Keep the core package dependency-free; add integrations as separate projects.

Suggested PR title format: feat: ... / fix: ... / chore: .... Use ! to denote breaking changes.

Licence

This project is licensed under MIT. See the LICENSE file for details.