MediatR Validation and the Chain of Responsibility Pattern

MediatR, Validation, and the Chain of Responsibility Pattern
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Hey everyone, I'm Steve Smith aka ardalis, of NimblePros!
In this video we take a look at how to pull validation out of our Web/UI layer and move it closer to our business/domain layer. We're using CQRS and MediatR with Clean Architecture to implement the Chain of Responsibility Pattern. The actual validation is using FluentValidation.
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[@fizmhd]

thanks for making videos, have been using your libraries, its great to see that you are on RUclips.

[@Ardalis]

Glad you like them!

[@joshuawilliams8230]

Your SOLID course on Pluralsight is so good! I also love your DDD course with Julie Lerman

[@Ardalis]

Thanks so much!

[@rezaabolhasanzadeh6845]

tnx Steve . I love your content and way of teaching . I'm surprised your channel has few subs . please be more active on youtube . your knowledge is really usefull

[@Ardalis]

Thanks! Aiming for weekly videos; we’ll see how it goes.

[@Ardalis]

Thanks! Aiming for weekly videos; we’ll see how it goes.

[@coderider3022]

Yip, definitely use it with a fluent result return type (validation error mapped to reason) and I return this as a failure instead of calling next.

[@Ardalis]

Agreed.

[@pavelernestonavarroguerrer7871]

Thanks a lot! An excelent and practical use of the behaviors!

[@Ardalis]

Glad you enjoyed it!

[@evilroxxx]

Hi Ardalis, love the segment. Do you think it would make sense to add fluent validation on every step sort of like an anti corruption layer within the layers of the clean architecture?

[@Ardalis]

I aim to do validation at the UI and/or app services (use cases) layer, and then use guard clauses and exceptions mainly in my domain modal. I have a video on *why* I make that distinction here: ruclips.net/video/dpPcnAT7n7M/видео.html&ab_channel=Ardalis

[@herewegotoday]

I currently use the template method pattern for ensuring multiple features always create an audit log for the task. Would the chain of responsibility pattern be better suited for such a thing? It certainly seems more elegant.

[@Ardalis]

It would almost certainly require less code and would eliminate inheritance, which usually simplifies designs. I'd say it's worth trying it and then you can assess which you prefer.

[@mesutdemirci7933]

Thanks a lot!

[@Ardalis]

You're welcome!