A lightweight and straightforward mediator implementation for .NET applications, facilitating in-process messaging with minimal setup.

Package	Version	Popularity
NetDevPack.SimpleMediator

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You can find complete example projects demonstrating how to use the SimpleMediator in the /samples folder.

These include:

• ✅ Basic usage with Send and Publish
• ✅ Modular application structure
• ✅ Manual and automatic registration of handlers

Feel free to explore and run them to see how the mediator works in different scenarios.

You can install the SimpleMediator package via NuGet Package Manager or the .NET CLI:

dotnet add package NetDevPack.SimpleMediator

To reference only the contracts for SimpleMediator, which includes:

• IRequest (including generic variants)
  • Represents a command or query that expects a single response
• INotification
  • Represents an event broadcast to multiple handlers (if any)

This example demonstrates how to combine a Request (command/query) and a Notification (event) in a real-world use case.

✅ This scenario uses only Microsoft.Extensions.DependencyInjection.Abstractions for DI registration — no framework-specific packages.

public class CreateCustomerCommand : IRequest<string>
{
    public string Name { get; set; }
}

public class CustomerCreatedEvent : INotification
{
    public Guid CustomerId { get; }

    public CustomerCreatedEvent(Guid customerId)
    {
        CustomerId = customerId;
    }
}

public class CreateCustomerHandler : IRequestHandler<CreateCustomerCommand, string>
{
    private readonly IMediator _mediator;

    public CreateCustomerHandler(IMediator mediator)
    {
        _mediator = mediator;
    }

    public async Task<string> Handle(CreateCustomerCommand request, CancellationToken cancellationToken)
    {
        var id = Guid.NewGuid();

        // Simulate persistence...

        // Publish event
        await _mediator.Publish(new CustomerCreatedEvent(id), cancellationToken);

        return $"Customer '{request.Name}' created with ID {id}";
    }
}

public class SendWelcomeEmailHandler : INotificationHandler<CustomerCreatedEvent>
{
    public Task Handle(CustomerCreatedEvent notification, CancellationToken cancellationToken)
    {
        Console.WriteLine($"Sending welcome email to customer {notification.CustomerId}");
        return Task.CompletedTask;
    }
}

You can register everything manually if you want full control:

services.AddSingleton<IMediator, Mediator>();

services.AddTransient<IRequestHandler<CreateCustomerCommand, string>, CreateCustomerHandler>();
services.AddTransient<INotificationHandler<CustomerCreatedEvent>, SendWelcomeEmailHandler>();

Or use assembly scanning with:

services.AddSimpleMediator();

public class CustomerAppService
{
    private readonly IMediator _mediator;

    public CustomerAppService(IMediator mediator)
    {
        _mediator = mediator;
    }

    public async Task<string> CreateCustomer(string name)
    {
        return await _mediator.Send(new CreateCustomerCommand { Name = name });
    }
}

When the CreateCustomer method is called:

1. CreateCustomerHandler handles the request
2. It creates and persists the customer (simulated)
3. It publishes a CustomerCreatedEvent
4. SendWelcomeEmailHandler handles the event

This structure cleanly separates commands (which change state and return a result) from notifications (which communicate to the rest of the system that something happened).

• Lightweight: Minimal dependencies and straightforward setup.
• In-Process Messaging: Facilitates in-process communication between components.
• Handler Registration: Automatically registers handlers from specified assemblies.

NetDevPack.SimpleMediator targets .NET Standard 2.1, and is compatible with .NET Core 3.1+, .NET 5+, .NET 6+, .NET 7+, .NET 8, and newer versions of the .NET runtime.

NetDevPack.SimpleMediator was developed by Eduardo Pires under the MIT license.