Advanced .NET Technique: Custom Attributes for PubSub Controllers

This project demonstrates an advanced usage of Custom Attributes in .NET to create a Publish-Subscribe system, similar to how REST API controllers function. Published in an article on Medium.

Overview

.NET Custom Attributes allow for declarative metadata annotations on class elements, which can be introspected at runtime using reflection. This project showcases their utility in dynamically wiring up a pub-sub message handling system.

Features

• Publisher: A component responsible for broadcasting messages over a named pipe.
• PubSubExtension: An extension class for IServiceCollection that autocovers and registers methods with the [Topic] attribute.
• Subscriber: A background service that listens for messages and triggers corresponding methods marked by the [Topic] attribute.
• SubscribeController: Base class for controllers with methods that can be invoked through pub-sub messaging.

Getting Started

To explore this example on your machine:

1. Clone the repository.
2. Ensure you have the .NET development environment set up.
3. Build and run the project in your preferred .NET-compatible IDE (like Visual Studio).

Start the Subscriber:

cd Subscriber
dotnet run

Start the Publisher

cd Publisher
dotnet run

# => start typing a message and send it by pressing 'Enter'
# * the Subscriber will receive the message

Usage

• Example Publish method invocation:

var publisher = new Publisher();
publisher.Publish("YourTopic", new YourMessageType { /* message data */ });

• Create a SubscribeController derived class:

public class YourController : SubscribeController
{
    [Topic("YourTopic")]
    public async Task<object> YourMessageHandler(YourMessageType message)
    {
        // Handle incoming message
    }
}

Ensure your derived controller class and its message-handling methods are accessible to the PubSubExtension logic.

• Integrate the pub-sub mechanism into your application's startup:

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers();
    services.AddPubSub(/* ApplicationName */);
}

Contributions

Feel free to fork, modify, and use this codebase as you see fit.

Resources

• For more clean code principles and practices, visit Clean Code Principles.