更新了 AutoMapper，现在收到未映射的属性异常

我有以下映射：

Mapper.CreateMap<Playlist, PlaylistDto>()
      .ReverseMap()
      .ForMember(playlist => playlist.Folder,
          opt => opt.MapFrom(playlistDto => folderDao.Get(playlistDto.FolderId)));

它将 Playlist 对象转换为 PlaylistDto 对象并返回。在我更新 AutoMapper 之前，它似乎工作得很好。

现在，当我打电话时：

Mapper.AssertConfigurationIsValid();

I see:

Unmapped members were found. Review the types and members below.
Add a custom mapping expression, ignore, add a custom resolver, or modify the source/destination type
=====================================================
PlaylistDto -> Playlist (Source member list)
Streamus.Dto.PlaylistDto -> Streamus.Domain.Playlist (Source member list)
-----------------------------------------------------
FolderId

Playlist 和 PlaylistD 看起来像：

[DataContract]
public class PlaylistDto
{
    [DataMember(Name = "id")]
    public Guid Id { get; set; }

    [DataMember(Name = "title")]
    public string Title { get; set; }

    [DataMember(Name = "folderId")]
    public Guid FolderId { get; set; }

    [DataMember(Name = "items")]
    public List<PlaylistItemDto> Items { get; set; }

    [DataMember(Name = "sequence")]
    public int Sequence { get; set; }

    public PlaylistDto()
    {
        Id = Guid.Empty;
        Title = string.Empty;
        Items = new List<PlaylistItemDto>();
    }

    public static PlaylistDto Create(Playlist playlist)
    {
        PlaylistDto playlistDto = Mapper.Map<Playlist, PlaylistDto>(playlist);
        return playlistDto;
    }
}

public class Playlist : AbstractShareableDomainEntity
{
    public virtual Folder Folder { get; set; }
    //  Use interfaces so NHibernate can inject with its own collection implementation.
    public virtual ICollection<PlaylistItem> Items { get; set; }
    public virtual int Sequence { get; set; }

    public Playlist()
    {
        Id = Guid.Empty;
        Title = string.Empty;
        Items = new List<PlaylistItem>();
        Sequence = -1;
    }
}

为什么AutoMapper更新后无法自动从Folder中派生FolderId？

请注意，即使我尝试显式定义到 FolderId 的映射，它仍然会抱怨：

Mapper.CreateMap<Playlist, PlaylistDto>()
       .ForMember(playlist => playlist.FolderId,
            opt => opt.MapFrom(playlistDto => playlistDto.Folder.Id))
      .ReverseMap()
      .ForMember(playlist => playlist.Folder,
            opt => opt.MapFrom(playlistDto => folderDao.Get(playlistDto.FolderId)));

答案是明确声明我的映射：

Mapper.CreateMap<Playlist, PlaylistDto>();
Mapper.CreateMap<PlaylistDto, Playlist>()
    .ForMember(playlist => playlist.Folder,opt => opt.MapFrom(playlistDto => folderDao.Get(playlistDto.FolderId)));