Code Clarification

[AERONAUT-AUT]

 Hi All, 

I´m a complete newcomer and trying to get all the Stuff together.

Could you please explain below mentioned Codelines ( of the BlazorHero Template) to me!?
what is the purpose of the:
*) await _cache.GetorAddAsync
*) _mapper.map
lines?

Furthermore i´m trying to get only the Name Column of the Brands Table, but can´t figure out a way.
public async Task<Result<List<GetAllBrandsResponse>>> Handle(GetAllBrandsQuery request, CancellationToken cancellationToken) { Func<Task<List<Brand>>> getAllBrands = () => _unitOfWork.Repository<Brand>().GetAllAsync(); var brandList = await _cache.GetOrAddAsync(ApplicationConstants.Cache.GetAllBrandsCacheKey, getAllBrands); var mappedBrands = _mapper.Map<List<GetAllBrandsResponse>>(brandList); return await Result<List<GetAllBrandsResponse>>.SuccessAsync(mappedBrands); }

Can you help me please?

[jeremiedevos]

Hi @AERONAUT-AUT,
To explain the code lines:

var brandList = await _cache.GetOrAddAsync(ApplicationConstants.Cache.GetAllBrandsCacheKey, getAllBrands);
The _cache.GetOrAddAsync is part of the lazycache (github) library that adds the functionality to cache data in asp.net/core.
In this case it will either get cashed data or add it to the cash.

var mappedBrands = _mapper.Map<List<GetAllBrandsResponse>>(brandList);
This is a way to map from one class to another when the properties are named the same.
Here is the library automapper used (see the owner his tutorial), so in this case it is mapping List<Brand> to List<GetAllBrandsResponse>.

To get only the name of the brand table you could make a new endpoint in the API controller and create a new command and so on... Then when you can dd in the repository a method that only returns the all the names or use the getall and only use the name property. In the response you can only return a list of all the names of the brands.

If you want to see how to add everything in the correct order, take a look at this discussion where there is a list with all the steps.

[AERONAUT-AUT]

Thanks a lot for your reply.

I already followed these instructions to add all my new entities/queries/controllers/.....
I thought I can use a linq statement to use only one attribute of an already existing entity instead of creating an new api endpoint & everything else.
I'm not sure if I'm maybe thinking completely wrong.

For the mapping item... you said, it maps the list to List.
Why is List not mentioned in the statement and what about (brandslist)?

[jeremiedevos]

Regarding the list to list. The naming is mappedbrands , note the s?. Note that the classes are different. By using automapper you don't have to initiate the class and populate it yourself. This is what the _mapper.Map does.

If we deconstruct this line of code:
var mappedBrands = _mapper.Map<List<GetAllBrandsResponse>>(brandList);

We make a variable named mappedBrands that will end up having an object of type List<GetAllBrandsResponse> just as mentioned in _mapper.Map<List<GetAllBrandsResponse>>.

When the variable brandlist was set, it was defined as List<Brand> (this is what the repository returns)

So you could see it like this:
var mappedBrands = _mapper.Map<{TARGETTYPE}>({CURRENT_POPULATION});

If that was not making anything nore clear you might want to take a look at the tutorial/blog i send earlier or do quick google to find what automapper is.