AutoMapper：限制嵌套模型中的行数

Question

I have a viewModel with lots of properties and a lot of collections of other viewModels

public ICollection<ListView> Elements { get; set; }

Can I specify somewhere that AutoMapper only takes the first 10 elements of this collection?

Answer 1

You could do a resolve using in your map. This would give you an opportunity to put in your own expression like so:

YourClassConstructorOrWhatever(){ 
    AutoMapper.Mapper.CreateMap<YourSourceObject, YourDestObject>()
          .ForMember(dest => dest.Elements, opt => opt.ResolveUsing(src =>
          {
              var result = new List<YourMapObject>();
              foreach (var element in src.Elements.Take(10))
              {
                        result.Add(Mapper.Map<YourMapObject>(element));
              }
                 return result;             
          }));
}

Resolve using in your mapping configuration allows you to specify how you want to map one thing to another.

More info and examples can be found here: https://github.com/AutoMapper/AutoMapper/wiki/Custom-value-resolvers

Mapper.Initialize(cfg => {
    cfg.CreateMap<Source, Destination>()
        .ForMember(dest => dest.Total,
            opt => opt.ResolveUsing<CustomResolver, decimal>(src => src.SubTotal));

    cfg.CreateMap<OtherSource, OtherDest>()
        .ForMember(dest => dest.OtherTotal, opt => opt.ResolveUsing<CustomResolver, decimal>(src => src.OtherSubTotal));
});

public class CustomResolver : IMemberValueResolver<object, object, decimal, decimal> {

    public decimal Resolve(object source, object destination, decimal sourceMember, decimal destinationMember, ResolutionContext context) {
        // your mapper logic here
    }
}

You could also use custom resolvers to do this: https://github.com/AutoMapper/AutoMapper/wiki/Custom-value-resolvers#customizing-the-source-value-supplied-to-the-resolver