Extension method for chaining requests

[awhisker]

Hello all,

My instinct tells me this is bad, but what are your views on extension method(s) which allow the chaining of MediatR requests as follows?

var response = await mediator
    .StartWith(new Request1())
    .Then(response1 => new Request2(response1));

• StartWith Initiates the "saga" by sending the first request.
• Then Allows you to chain additional requests based on the response of the previous step.

Below is the initial implementation of the extension methods (needs to be updated to allow multiple Then() chains):

public static class MediatRExtensions
{
    public static MediatorChain<TResponse> StartWith<TResponse>(this IMediator mediator, IRequest<TResponse> request, CancellationToken cancellationToken = default)
    {
        var responseTask = mediator.Send(request, cancellationToken);

        return new MediatorChain<TResponse>(mediator, responseTask);
    }
}

public class MediatorChain<TResponse>
{
    private readonly IMediator _mediator;
    private readonly Task<TResponse> _responseTask;

    public MediatorChain(IMediator mediator, Task<TResponse> responseTask)
    {
        _mediator = mediator;

        _responseTask = responseTask;
    }

    public async Task<TNextResponse> Then<TNextResponse>(Func<TResponse, IRequest<TNextResponse>> createRequest, CancellationToken cancellationToken = default)
    {
        var response = await _responseTask;

        var request = createRequest(response);

        return await _mediator.Send(request, cancellationToken);
    }
}

Thank you!