Cannot map from nullable type using ForCtorParam

[TannerStrike]

Hello,

I am running into an issue when trying to map from a decimal? to a nullable type. Here is my setup:

// source object
public sealed class Offer {
    public Offer(decimal? minTransactionAmount) {
        MinTransactionAmount = minTransactionAmount;
    }

    public decimal? MinTransactionAmount { get; }
}

// destination
public record CatalogDetails(CatalogAmount? MinTransactionAmount);
public record CatalogAmount([property: JsonConverter(typeof(DecimalToStringJsonConverter))] decimal Amount, Currencies Currency);
public enum Currencies : byte {
    Usd = 0,
}

// mapping logic
CreateMap<Offer, CatalogDetails>()
    .ForCtorParam(nameof(CatalogDetails.MinTransactionAmount), opt => opt.MapFrom(src => getCatalogAmount(src.MinTransactionAmount)));

private static CatalogAmount? getCatalogAmount(decimal? amount) =>
    amount.HasValue ? new CatalogAmount(amount.Value, Currencies.Usd) : null;

As you can see, all I want to do is simply map decimal? value on Offer to a CatalogAmount?, however I am getting this exception:

AutoMapper.AutoMapperMappingException: Unable to create a map expression from Offer.MinTransactionAmount (System.Nullable`1[System.Decimal]) to CatalogAmount.MinTransactionAmount (ZapMiddleware.RewardCatalog.Contracts.Catalog.CatalogAmount)\n\nMapping types:\nOffer -> CatalogDetails\nZapMiddleware.RewardCatalog.Domain.Offers.Offer -> ZapMiddleware.RewardCatalog.Contracts.Catalog.CatalogDetails\n\nType Map configuration:\nOffer -> CatalogDetails\nZapMiddleware.RewardCatalog.Domain.Offers.Offer -> ZapMiddleware.RewardCatalog.Contracts.Catalog.CatalogDetails\n\nDestination Member:\nZapMiddleware.RewardCatalog.Contracts.Catalog.CatalogDetails.Void .ctor(Int32, Int32, System.Guid, Int64, Int64, System.String, ZapMiddleware.RewardCatalog.Contracts.Catalog.CatalogAmount, Boolean, ZapMiddleware.RewardCatalog.Contracts.Catalog.CatalogReward).parameter MinTransactionAmount

All I can determine is that there is some issue with mapping from a nullable type using ForCtorParam? I have tried numerous null-checks, but cannot get this to work.

Any ideas?

[TannerStrike]

I ended up getting this to work if I change the code to this:

public record CatalogDetails(CatalogAmount? MinTransactionAmountzzz); //with zzz at the end

CreateMap<Offer, CatalogDetails>()
    .ForCtorParam(nameof(CatalogDetails.MinTransactionAmountzzz), opt => opt.MapFrom(src => getCatalogAmount(src.MinTransactionAmount)));

Its like I am manually setting up the mapping, but AutoMapper is still trying to automap from decimal -> CatalogAmount, which of course cannot be automapped and causes an exception?

[lbargaoanu]

https://docs.automapper.org/en/latest/Queryable-Extensions.html#supported-mapping-options
https://docs.automapper.org/en/latest/11.0-Upgrade-Guide.html#createprojection