Dom.Mediator 1.0.1

Dom.Mediator

Dom.Mediator is a clean, minimal implementation of the Mediator pattern for .NET, focused on:

• ✅ Request/Response messaging (CQRS)
• ✅ Composable pipeline behaviors (validation, logging, etc.)
• ✅ Built-in Result Pattern handling with typed errors
• ✅ Lightweight with minimal dependencies
• ✅ Perfect fit for Minimal APIs or Clean Architecture

📦 Install via NuGet

dotnet add package Dom.Mediator

🚀 Quick Example

Commands (Actions without return values)

Define your command:

public record CreateTaskCommand(string Title, string? Description) : ICommand;

Create a handler:

public class CreateTaskHandler : ICommandHandler<CreateTaskCommand>
{
    public Task<Result> Handle(CreateTaskCommand command, CancellationToken cancellationToken)
    {
        // Perform action logic here
        return Task.FromResult(Result.Success());
    }
}

Queries (Read operations with return values)

Define your query:

public record GetTasksQuery() : IQuery<List<TaskItem>>;

Create a handler:

public class GetTasksHandler : IQueryHandler<GetTasksQuery, List<TaskItem>>
{
    public Task<Result<List<TaskItem>>> Handle(GetTasksQuery query, CancellationToken cancellationToken)
    {
        var tasks = GetTasksFromStore(); // Your logic here
        return Task.FromResult(Result<List<TaskItem>>.Success(tasks));
    }
}

Setup with Dependency Injection

builder.Services.AddMediator(config =>
{
    config.RegisterHandlers(typeof(Program).Assembly);
    
    // Add pipeline behaviors
    config.AddRequestResponseBehaviour(typeof(LoggingBehaviour<,>));
    config.AddCommandBehaviour(typeof(ValidationBehaviour<>));
});

📚 Samples & Examples

Check out the samples directory for complete working examples:

🧪 Testing: See the tests directory for unit tests, coverage reports, and testing documentation.

🌐 Minimal API Sample

A complete ASP.NET Core Minimal API implementation demonstrating:

• Task Management API with CQRS pattern
• Command & Query handlers with validation
• Pipeline behaviors for logging and cross-cutting concerns
• Result pattern integration with HTTP responses
• Swagger documentation and endpoint configuration

cd samples/Dom.Mediator.Samples.MinimalApi
dotnet run

⚙️ Built-in Features

• 🧱 Pipeline Behaviors: Add logging, validation, error handling in a clean chain
• 🎯 Result Pattern: Native success/failure with structured error codes (Result<T> and Result)
• 🔄 Auto-Handler Discovery: Reflective scanning via assembly registration
• 💡 CQRS Support: Separate Command and Query handling with distinct interfaces
• 🏗️ Dependency Injection: Built-in support for Microsoft DI container

🧩 Pipeline Behaviors

Add behaviors to intercept and process requests:

// For queries (request/response)
config.AddRequestResponseBehaviour(typeof(LoggingBehaviour<,>));

// For commands
config.AddCommandBehaviour(typeof(ValidationBehaviour<>));

Request/Response Behavior Interface:

public interface IPipelineBehavior<TRequest, TResponse>
    where TRequest : IRequest<TResponse>
{
    Task<Result<TResponse>> Handle(
        TRequest request, 
        CancellationToken cancellationToken, 
        RequestHandlerDelegate<TResponse> next);
}

Command Behavior Interface:

public interface IPipelineBehavior<TCommand>
    where TCommand : ICommand
{
    Task<Result> Handle(
        TCommand command, 
        CancellationToken cancellationToken, 
        CommandHandlerDelegate next);
}

📜 License

Dom.Mediator is MIT licensed.

👤 Author

Made with ❤️ by André Dominic Santacroce