Use Case: Migrating from MediatR to SlimMessageBus

The SlimMessageBus in-memory provider can replace the need to use the MediatR library:

It has similar semantics and has the interceptor pipeline enabling the addition of custom behavior.
The generic interceptors can introduce common behavior like logging, authorization, or audit of messages.
The FluentValidation plugin can introduce request/command/query validation.
The external communication can be layered on top of SlimMessageBus, enabling one library for in-memory and out-of-process messaging (Hybrid Provider).

See the CQRS and FluentValidation samples.

Example: Migrating from MediatR to SlimMessageBus

Below are examples demonstrating the migration steps.

Using MediatR in `Program.cs`

Here is a typical setup for MediatR:

using MediatR;

var builder = WebApplication.CreateBuilder(args);

// Register MediatR services
builder.Services.AddMediatR(cfg =>
{
    cfg.RegisterServicesFromAssemblyContaining<Program>();
});

var app = builder.Build();

app.MapGet("/ping", async (IMediator mediator) =>
{
    return await mediator.Send(new PingRequest());
});

app.Run();

// Define a simple request and handler
public record PingRequest : IRequest<string>;

public class PingRequestHandler : IRequestHandler<PingRequest, string>
{
    public Task<string> Handle(PingRequest request, CancellationToken cancellationToken)
    {
        return Task.FromResult("Pong");
    }
}

Migrating to SlimMessageBus in `Program.cs`

Install required NuGet packages:

dotnet add package SlimMessageBus.Host.Memory

Example code setup:

using SlimMessageBus;
using SlimMessageBus.Host.Memory;

var builder = WebApplication.CreateBuilder(args);

// Configure SlimMessageBus with In-Memory provider
builder.Services.AddSlimMessageBus(mbb =>
{
    mbb.WithProviderMemory().AutoDeclareFrom(typeof(Program).Assembly);
});

var app = builder.Build();

app.MapGet("/ping", async (IMessageBus bus) =>
{
    return await bus.Send(new PingRequest());
});

app.Run();

// Define request and handler compatible with SlimMessageBus
public record PingRequest : IRequestMessage<string>;

public class PingRequestHandler : IRequestHandler<PingRequest, string>
{
    public async Task<string> OnHandle(PingRequest request, CancellationToken cancellationToken)
    {
        return "Pong";
    }
}

Key Changes:

Replace IMediator with IMessageBus.
Change request interface from IRequest to IRequestMessage.
Register SlimMessageBus using AddSlimMessageBus and configure with WithProviderMemory.
Handlers now implement IRequestHandler<TRequest, TResponse> with method OnHandle() instead of MediatR’s Handle().

Additional Capabilities in SlimMessageBus:

Interceptors: You can easily add cross-cutting concerns such as logging, authorization, or auditing.
FluentValidation Integration: Direct support for request validation via FluentValidation.
Hybrid Messaging: Seamlessly transition from in-memory to out-of-process messaging if your application evolves (or combine both).

For more advanced usage and additional features, please review the SlimMessageBus documentation.

Hybrid Messaging: Seamlessly transition from in-memory to out-of-process messaging if your application evolves (or combine both).