Getting started

Mediant targets .NET 8, 9 and 10.

1. Install

dotnet add package Mediant

Optional packages, added as you need them:

Package	What it adds
`Mediant.Behaviors`	The 11 built-in pipeline behaviors
`Mediant.FluentValidation`	FluentValidation integration (auto-discovery, multi-validator)
`Mediant.AspNetCore`	`[HttpEndpoint]` mapping, Result-to-HTTP, OpenAPI
`Mediant.SourceGenerator`	Compile-time, AOT-safe registration & dispatch
`Mediant.EntityFrameworkCore`	Durable EF Core stores for the outbox and audit
`Mediant.Analyzers`	Roslyn analyzers that catch attribute misuse at compile time
`Mediant.Contracts`	Shared contracts for multi-project solutions

2. Register

builder.Services.AddMediant(cfg =>
    cfg.RegisterServicesFromAssembly(typeof(Program).Assembly));

3. Define a command

Commands change state; queries read it. Mediant makes that explicit.

public record CreateOrderCommand(string UserId, List<OrderItem> Items)
    : ICommand<Result<Guid>>;

4. Handle it

Handlers return ValueTask<T> and carry failures in a Result<T> — no exceptions for control flow.

public class CreateOrderHandler : ICommandHandler<CreateOrderCommand, Result<Guid>>
{
    public ValueTask<Result<Guid>> Handle(CreateOrderCommand request, CancellationToken ct)
    {
        var orderId = Guid.NewGuid();
        // ... create the order
        return new ValueTask<Result<Guid>>(Result<Guid>.Success(orderId));
    }
}

5. Send it

var result = await mediator.Send(new CreateOrderCommand("user-1", items));

result.Match(
    id => Console.WriteLine($"Order created: {id}"),
    error => Console.WriteLine($"Failed: {error.Description}"));

Configuration

builder.Services.AddMediant(cfg =>
{
    cfg.RegisterServicesFromAssembly(typeof(Program).Assembly);
    cfg.NotificationPublishStrategy = NotificationPublishStrategy.Parallel;
    cfg.EnablePolymorphicNotifications = true;
    cfg.ValidateOnStartup = true;                       // fail fast on a missing handler

    cfg.AddOpenBehavior(typeof(MyLoggingBehavior<,>));  // wraps every request
});

builder.Services.AddMediantValidation(typeof(Program).Assembly);
builder.Services.AddMediantAllBehaviors();

Namespaces

using Mediant.Abstractions;   // ICommand, IQuery, handlers, behaviors
using Mediant.Results;        // Result<T>, Error, ErrorType

Next steps

Commands & queries — the CQRS surface.
The Result pattern — errors without exceptions.
Pipeline behaviors — the 11 built-ins.
Coming from MediatR? Migrate in a few steps.