Place and use of MediatR code and Specification code

[hansmbakker]

Hi,

thank you for this great starter repository and for the series of blog articles! I'm still finding my way how to best structure a DDD/CQRS project and your content is really helpful for that.

I was hoping you could help me understand the place and use of the MediatR code and Specification code better.

• I am wondering why the MediatR code (models, queries, commands) is part of the Web API project and not of the Core (domain model) project and the Infrastructure?
  E.g. this blog puts the MediatR Commands & Queries in the Domain project, and the IRequestHandler implementations in the Services (infrastructure) project:
  https://medium.com/@ducmeit/net-core-using-cqrs-pattern-with-mediatr-part-1-55557e90931b
  https://medium.com/@ducmeit/net-core-using-cqrs-pattern-with-mediatr-part-2-cc55763e83f0
  https://github.com/ducmeit1/cqrswithmediatr

You put the Specifications in the Core (domain model) project; this seems similar to how the blog I linked above puts Queries in its Domain project.

• shouldn't the CosmosDbSpecificationEvaluator be in the Infrastructure project then, given that that is likely going to be a specific implementation?
• I see MediatR being used in the Web API project, and Specifications being used in the Functions project. Can you please explain something about when you choose to use MediatR, and when you choose to use Specifications?

[SKharayat]

@hansmbakker MediatR command and queries responsibility is to orchestrate the application flow and let the information flow from application layer to infrastructure (referencing core layer or models ) and finally to the database, this is the reason I myself keep them in application layer, also as Dto's are not a part of core (as per my view) they also act as ACL's in DDD so they do not need to flow via core layer they can be used in mediatR queries for fetching read-only data in this case also I feel queries should be application layer.
I am myself struggling with structuring CQRS/DDD in my api's, please let me know your views on my inputs and if you have any suggestions that will be awesome .