Supply additional parameters to the mapping method

Sometimes you want to provide an external value to the mapping method. For example your DTO doesn’t have a tenant id. You are getting the tenant id from the currently signed in user and it’s the same for every entity inside the current request.

[Mapper]
public partial class CarMapper
{
    public partial Car Map(CarDto dto, string tenantId);
}

public record Car(string Name, string TenantId);

public record CarDto(string Name);

Example usage:

    public void UseMapper(CarMapper mapper, IEnumerable<CarDto> dtos)
    {
        string tenantId = ""; //GetFromDb;
        var entities = dtos.Select(dto => mapper.Map(dto, tenantId));
    }

You could accomplish this by moving TenantId to a property and using the after map feature. But I think this solution is cleaner. It doesn’t force you to change your domain code for a mapper, it shows the intent more clearly and it’s simpler to add.

[latonz]

@Fube I don’t think flattening/unflattening would be the right approach for this, it could work as a workaround though. IMO the way to go would either be providing parameters directly to the mapping methods which are then mapped by name to properties of the target object or to add a secondary source objects which are also considered as mapping sources.

[DerMave]

@latonz I haven’t really gotten around to it yet. I made some unit tests and looked at the relevant bits and pieces. It seems I have underestimated the scope of this change. I am still interested in going forward with it, but I have to find some free time.