C#: How do you implement the mediator pattern?

1// Request
2public record CreateOrderCommand(string Product) : IRequest<int>;
3
4// Handler
5public class CreateOrderHandler(IOrderService svc)
6    : IRequestHandler<CreateOrderCommand, int>
7{
8    public async Task<int> Handle(
9        CreateOrderCommand request, CancellationToken ct)
10    {
11        return await svc.CreateAsync(request.Product);
12    }
13}

1var orderId = await mediator.Send(new CreateOrderCommand("Widget"));