The specification must have Selector defined - how is it mapped to a dto?

[ThomasVague]

Hi, quick question.

I'm trying to implement some of the pagination features into my own project, and I get this error when I try to use a specification with the <T, TResult> implementation. When I add a Select statement to the specification, and map the properties, it works fine.
But in the FSH repo there is no Select, it just does the mapping without any error. I only have two properties in my entity and dto; Id and Description, and they are of the same types, so I just find it puzzing that it's not working for me. I've copied over the "base" specifcations and extensions used, so everything is the same.

[fretje]

How are you using the specification exactly?

You shouldn't have to do a "select"... that happens behind the scenes by using a specification that has 2 type parameters. (In our implementation it actually uses mapster's projectToType method, so the mapping is actually done when querying the database. ==> see ApplicationDbRepository.ApplySpecification)

But when using the GetBySpecAsync method, you have to cast the spec so the right overload is used:

        await _repository.GetBySpecAsync(
            (ISpecification<Brand, BrandDto>)new BrandByIdSpec(request.Id), cancellationToken)

Maybe that is the culprit?

[ThomasVague]

Thanks! The culprit was the ApplySpecifcation missing in the Repository class. I haven't used the GetBySpec function. Only the List and the PaginatedListAsync where it's not explicitly casted.