TrimKit.EventBus

A lightweight and mutation-safe event bus (event aggregator) for C# applications and games. Designed for simplicity and ease of use.

TrimKit.EventBus allows different parts of your system to communicate via strongly-typed events without hard dependencies or direct references.

Features

• Lightweight & dependency-free.
• Thread-safe.
• Mutation-safe - handlers can safely modify subscriptions even during event publishing.
• Disposable subscriptions - each Subscribe() returns an IDisposable token for easy unsubscribe.
• SubscribeOnce() support - automatically unsubscribes after first event.
• Duplicate protection - prevents duplicate handler registration.

Installation

Use provided nuget package or download the source.

🔧 dotnet add package TrimKit.EventBus

Quick start

Define your events:

public sealed class GameStartedEvent
{
    public DateTime StartTime { get; }
    public GameStartedEvent(DateTime startTime) => StartTime = startTime;
}

public sealed class CharacterDamagedEvent
{
    public string Name { get; }
    public int Damage { get; }
    public CharacterDamagedEvent(string name, int damage)
    {
        Name = name;
        Damage = damage;
    }
}

Create the event bus itself:

var bus = new EventBus();

Add subscribers. You can subscribe normally or use SubscribeOnce() for a one-time handler.

// normal subscription
var token = bus.Subscribe<CharacterDamagedEvent>(e =>
{
    Console.WriteLine($"{e.Name} took {e.Damage} damage!");
});

// subscribe once
bus.SubscribeOnce<GameStartedEvent>(e =>
{
    Console.WriteLine($"[Once] Game started at {e.StartTime:T}");
});

Each Subscribe() returns an IDisposable token you can later call Dispose() on to unsubscribe:

token.Dispose();

And now you can start publishing events:

bus.Publish(new GameStartedEvent(DateTime.Now));
bus.Publish(new CharacterDamagedEvent("Goblin", 25));

Thread safety

All operations (Subscribe, Unsubscribe, Publish, Reset) are protected by a lock and safe for concurrent use. During event dispatch, handlers are called using a snapshot copy, so you can safely modify subscriptions while publishing.

Event dispatch rules

• Dispatch is by exact event type - base or interface subscribers do not receive derived events.
• Events can be any class or struct (no need for EventArgs).
• Handlers are simple Action<T> delegates without a sender parameter. You can include the sender information inside the payload itself.

API Overview

Method	Description
IDisposable Subscribe<T>(Action<T> handler)	Subscribe to event T.
IDisposable SubscribeOnce<T>(Action<T> handler)	Subscribe for one-time delivery.
bool Unsubscribe<T>(Action<T> handler)	Remove specific subscription.
void Publish<T>(T payload)	Publish event to all subscribers.
int GetSubscriberCount<T>()	Get count of current subscribers for a type.
bool HasSubscribers<T>()	Check if any subscribers exist.
void Clear<T>()	Remove all subscriptions for a type T.
void ClearAll()	Remove all subscriptions.

Changes

• v1.1 - Switched to using Actions and expanded API.
• v1.0.1 - Fixed namespaces.
• v1.0 - Initial release.

TrimKit Collection

This library is part of the TrimKit collection - a set of small, focused C# libraries that make game development more enjoyable by reducing the need for boilerplate code and providing simple reusable building blocks that can be dropped into any project.

• TrimKit.EventBus - Lightweight, mutation-safe event bus (event aggregator).
• TrimKit.GameSettings - JSON-based persistent settings manager.
• TrimKit.VirtualFileSystem - Unified file hierarchy abstraction to enable modding and additional content in games.
• TrimKit.StatDictionary - Simple character stat container for RPG or other games relying on stat heavy calculations.

Each module is independent and can be used standalone or combined with others for a complete lightweight foundation.

Contribution

Contributions are welcome!

You can start with submitting an issue on GitHub.

License

This library is released under the MIT License.