Implicit cast array

Question

I have two classes that are atm that same and defined cast:

 public static implicit operator SponsoredBrandViewModel(SponsoredBrand sponsoredBrand)
        =>
            new SponsoredBrandViewModel
            {
                Id = sponsoredBrand.Id,
                BrandId = sponsoredBrand.RelatedEntityId,
                To = sponsoredBrand.To,
                From = sponsoredBrand.From,
                Importance = sponsoredBrand.Importance
            };
    public static implicit operator SponsoredBrand(SponsoredBrandViewModel sponsoredBrandViewModel)
        =>
            new SponsoredBrand
            {
                Id = sponsoredBrandViewModel.Id,
                RelatedEntityId = sponsoredBrandViewModel.BrandId,
                To = sponsoredBrandViewModel.To,
                From = sponsoredBrandViewModel.From,
                Importance = sponsoredBrandViewModel.Importance
            };

I want to make it cast when it's a array.

ar dbSponsoredBrands = await this._sponsoredBrandRepository.GetAsync();
            var viewModels = (IEnumerable<SponsoredBrandViewModel>) dbSponsoredBrands.ToEnumerable();

But this throwing invalidcast exception.

Any ideas?

Chris Pickford · Accepted Answer · 2017-06-14 09:12:38Z

2

You're trying to cast the collection object IEnumerable<SponsoredBrand> into an IEnumerable<SponsoredBrandViewModel> where you've defined your implicit cast operator for the actual object. You'll need to iterate through the collection and create a new one, e.g.

var dbSponsoredBrands = await this._sponsoredBrandRepository.GetAsync();
var viewModels = dbSponsoredBrands.Select(x => (SponsoredBrandViewModel)x);

answered Jun 14, 2017 at 9:12

Chris Pickford

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2 Comments

Nerf Over a year ago

Yes, so no option to do it without iterating.

Chris Pickford Over a year ago

Correct, each object must be individually cast. If iterating presents a performance issue, you could take a lazy approach to the cast and defer it to when each viewmodel is used rather than all at once. Look into Enumerable.Cast<TResult> for more information.

ChriPf · Accepted Answer · 2017-06-14 11:15:38Z

0

You can use the LINQ-Functions

.Cast<SponsoredBrandViewModel>()

or

.OfType<SponsoredBrandViewModel>()

to achieve that. These will iterate over the result too, but in a lazy way. Use the first one if you are sure every element is of this type, the later one if you want to filter only the matching elements.

answered Jun 14, 2017 at 11:15

ChriPf

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