https://github.com/jbogard/MediatR/wiki#basics

Basics

MediatR has two kinds of messages it dispatches:

• Request/response messages, dispatched to a single handler
• Notification messages, dispatched to multiple handlers

 

Request/response

The request/response interface handles both command and query scenarios. First, create a message:

public class Ping : IRequest<string> { }

Next, create a handler:

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

Finally, send a message through the mediator:

var response = await mediator.Send(new Ping());
Debug.WriteLine(response); // "Pong"