AutoMapper 映射导航 属性 问题

Question

我正在关注这个答案 AutoMapper mapping int[] or List<int> from ViewModel to a List<Type> in Domain Model 并已将其与我的 CategoryId 绑定到 UploadSongViewModel 上的 SelectedCategoryIds，但是我也想将其绑定SongId 至 Id UploadSongViewModel。

namespace App
{
    public static class AutoMapper
    {
        public static MapperConfiguration Config;

        public static void Initialize()
        {
            //It works with CategoryId, but throws an error when I include SondId.
            Config = new MapperConfiguration(x =>
            {
                x.CreateMap<int, SongCategory>()
                    .IgnoreAllNonExisting()
                    .ForMember(dest => dest.CategoryId, opt => opt.MapFrom(src => src))
                    .ForMember(dest => dest.SongId, opt => opt.MapFrom(src => src)); //Code that's throwing exception

                x.CreateMap<UploadSongViewModel, Song>()
                    .IgnoreAllNonExisting()
                    .ForMember(dest => dest.AudioName, opt => opt.MapFrom(src => src.SongName))
                    .ForMember(dest => dest.AudioPath, opt => opt.MapFrom(src => src.SongPath))
                    .ForMember(dest => dest.SongCategories, opt => opt.MapFrom(src => src.SelectedCategoryIds))
                    .ForMember(dest => dest.SongCategories, opt => opt.MapFrom(src => src.Id)); //Code that's throwing exception
            });

            //Throws exception here because it can't bind SongId property
            Config.AssertConfigurationIsValid(); 
        }
    }
}

public abstract class Entity
{
    public int Id { get; set; }
}

public class SongCategory : Entity
{
    public int SongId { get; set; }
    public int CategoryId { get; set; }
}

public class Song : Audio
{
    public string AlbumName { get; set; }
    public string ArtistName { get; set; }

    public List<SongCategory> SongCategories { get; set;}
}

public class UploadSongViewModel
{
    public int Id { get; set; }
    public string ArtistName { get; set; }
    public string AlbumName { get; set; }
    public int[] SelectedCategoryIds { get; set; }

    public MultiSelectList CategoriesSelectList { get; set; }
}

我不太明白自动映射器代码在 Darin Dimitrov 的回答中做了什么，所以很难调试。如果有人可以解释此映射如何适用于 categoryId 以及为什么它不适用于 SongId，那就太好了。

我得到的异常是：

The following property on System.Collections.Generic.List1[[SoundVast.Models.SongCategory, SoundVast, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]] cannot be mapped: SongCategories Add a custom mapping expression, ignore, add a custom resolver, or modify the destination type System.Collections.Generic.List1[[SoundVast.Models.SongCategory, SoundVast, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]. Context: Mapping to property SongCategories from System.Int32 to System.Collections.Generic.List`1[[SoundVast.Models.SongCategory, SoundVast, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]] Mapping from type SoundVast.Areas.Upload.Models.UploadSongViewModel to SoundVast.Models.Song Exception of type 'AutoMapper.AutoMapperConfigurationException' was thrown.

Answer 1

一旦应用了基本规则，这可以通过一些自定义映射轻松实现：

x.CreateMap<int, SongCategory>()
    .IgnoreAllNonExisting()
    .ForMember(dest => dest.CategoryId, opt => opt.MapFrom(src => src));

x.CreateMap<UploadSongViewModel, Song>()
    .IgnoreAllNonExisting()
    .ForMember(dest => dest.AudioName, opt => opt.MapFrom(src => src.SongName))
    .ForMember(dest => dest.AudioPath, opt => opt.MapFrom(src => src.SongPath))
    .ForMember(dest => dest.SongCategories, opt => opt.MapFrom(src => src.SelectedCategoryIds))
    .AfterMap((viewModel, model) => 
    {
        foreach (var item in model.SongCategories)
        {
            item.Id = viewModel.Id;
        }
    });