What is MediatR and how does it relate to Clean Architecture?

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ICSM Computer · Answer

🧭 What is MediatR?
MediatR is a simple and lightweight .NET library that implements the
Mediator Pattern, which helps reduce tight coupling between components by centralizing communication.
In MediatR:
Requests (Commands or Queries) are sent to a mediator instead of calling services or logic directly.The mediator then invokes the appropriate handler.
NuGet Package:
Install-Package MediatR.Extensions.Microsoft.DependencyInjection
Basic MediatR Flow
Controller → MediatR.Send(request) → Handler → Business Logic → Response
Example
1. Define a Command (write action)
public record CreateStudentCommand(string Name, string Email) : IRequestandlt;boolandgt;;
2. Define a Handler
public class CreateStudentHandler : IRequestHandlerandlt;CreateStudentCommand, boolandgt;
{
    private readonly AppDbContext _db;
    public CreateStudentHandler(AppDbContext db) =andgt; _db = db;
    public async Taskandlt;boolandgt; Handle(CreateStudentCommand request, CancellationToken ct)
    {
        _db.Students.Add(new Student { Name = request.Name, Email = request.Email });
        await _db.SaveChangesAsync();
        return true;
    }
}
3. Send from Controller
public class StudentsController : ControllerBase
{
    private readonly IMediator _mediator;
    public StudentsController(IMediator mediator) =andgt; _mediator = mediator;
    [HttpPost]
    public async Taskandlt;IActionResultandgt; CreateStudent(CreateStudentCommand command)
    {
        var result = await _mediator.Send(command);
        return Ok(result);
    }
}
MediatR + Clean Architecture
Clean Architecture separates the system into layers:
[ Presentation ]
[ Application  ] ← Business rules (Application layer, UseCases)
[ Domain       ] ← Core business models/rules
[ Infrastructure ] ← EF Core, Email, External APIs, etc.
How MediatR Fits In:
Clean Architecture Layer
Role of MediatR
Application Layer
Hosts MediatR requests and handlers (CQRS)
Presentation Layer
Sends requests via IMediator.Send(...)
Infrastructure
Injected dependencies consumed by handlers
Benefits:
Encourages Single Responsibility per handlerKeeps Controllers thinPromotes decoupling of business logic from delivery (controller/UI)Facilitates unit testing of handlersNatural fit for CQRS (Command Query Responsibility Segregation)
CQRS + MediatR + Clean Architecture (Typical Pattern)
[ API Controller ]
        ↓
[ IMediator.Send() ]
        ↓
[ Command / Query Handler ]
        ↓
[ Application Services / Repositories ]
Summary
Aspect
MediatR
Pattern
Mediator
Used for
Decoupling request handling
Works well with
Clean Architecture and CQRS
Pros
Decouples logic, testable, modular
Common Use
Handle Commands and Queries

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What is MediatR and how does it relate to Clean Architecture?

ICSM Computer

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1 Answers

🧭 What is MediatR?

Basic MediatR Flow

Example

1. Define a Command (write action)

2. Define a Handler

3. Send from Controller

MediatR + Clean Architecture

How MediatR Fits In:

Benefits:

CQRS + MediatR + Clean Architecture (Typical Pattern)

Summary

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Clean Architecture Layer	Role of MediatR
Application Layer	Hosts MediatR requests and handlers (CQRS)
Presentation Layer	Sends requests via `IMediator.Send(...)`
Infrastructure	Injected dependencies consumed by handlers

Aspect	MediatR
Pattern	Mediator
Used for	Decoupling request handling
Works well with	Clean Architecture & CQRS
Pros	Decouples logic, testable, modular
Common Use	Handle Commands & Queries