带有 Linq OrderBy child 属性错误的 Automapper 投影

Question

我在使用 AutoMapper（版本 5.1.1）投影和 Linq OrderBy Child 属性表达式时遇到问题。我正在使用 Entity Framework 核心（版本 1.0.0）。我收到以下错误：

"must be reducible node"

我的DTO对象如下

public class OrganizationViewModel
    {
        public virtual int Id { get; set; }
        [Display(Name = "Organization Name")]
        public virtual string Name { get; set; }
        public virtual bool Active { get; set; }
        public virtual int OrganizationGroupId { get; set; }
        public virtual string OrganizationGroupName { get; set; }
        public virtual int StrategyId { get; set; }
        public virtual string StrategyName { get; set; }
        public virtual OrganizationGroupViewModel OrganizationGroup { get; set; }
    }

public class OrganizationGroupViewModel
    {
        public virtual int Id { get; set; }
        [Display(Name = "Organization Group Name")]
        public virtual string Name { get; set; }
        public virtual bool Active { get; set; }
    }

我对应的实体模型如下：

public class Organization
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string TimeZone { get; set; }
        public bool Active { get; set; }
        //FKs
        public int OrganizationGroupId { get; set; }
        public int StrategyId { get; set; }
        //Navigation
        public virtual OrganizationGroup OrganizationGroup { get; set; }
        public virtual Strategy Strategy { get; set; }
        [JsonIgnore]
        public virtual List<AppointmentReminder> AppointmentReminders { get; set; }
    }

public class OrganizationGroup
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public bool Active { get; set; }

        public virtual List<Organization> Organizations { get; set; }
    }

我的 AutoMapper 配置文件如下：

public class OrganizationMapperProfile : Profile
    {
        public OrganizationMapperProfile()
        {
            CreateMap<Task<Organization>, Task<OrganizationViewModel>>();
            CreateMap<Organization, OrganizationViewModel>()
                .ForMember(dest => dest.OrganizationGroupName, opt => opt.MapFrom(src => src.OrganizationGroup.Name));
            CreateMap<OrganizationInput, Organization>()
                .ForMember(x => x.Id, opt => opt.Ignore());
        }
    }

public class OrganizationGroupMapperProfile : Profile
    {
        public OrganizationGroupMapperProfile()
        {
            CreateMap<Task<OrganizationGroup>, Task<OrganizationGroupViewModel>>();
            CreateMap<OrganizationGroup, OrganizationGroupViewModel>();
            CreateMap<OrganizationGroupInput, OrganizationGroup>()
                .ForMember(x => x.Id, opt => opt.Ignore());
        }
    }

当我运行以下语句时，我能够运行并从前 2 个语句中获得结果：

var tmp = await _context.Organizations.Include(x => x.OrganizationGroup).OrderBy(x => x.OrganizationGroup.Name).ToListAsync();
var tmp4 = await _context.Organizations.Include(x => x.OrganizationGroup).OrderBy("OrganizationGroup.Name").ToListAsync();

但是当我添加 ProjectTo 时，出现上面列出的错误：

var tmp5 = await _context.Organizations.Include(x => x.OrganizationGroup).OrderBy(x => x.OrganizationGroup.Name).ProjectTo<OrganizationViewModel>().ToListAsync();
var tmp6 = await _context.Organizations.Include(x => x.OrganizationGroup).OrderBy("OrganizationGroup.Name").ProjectTo<OrganizationViewModel>().ToListAsync();

作为一些附加信息，我可以使用 OrderBy 和 Projections 处理父 class 的属性，例如：

var tmp7 = await _context.Organizations.Include(x => x.OrganizationGroup).OrderBy(x => x.Name).ProjectTo<OrganizationViewModel>().ToListAsync();
var tmp8 = await _context.Organizations.Include(x => x.OrganizationGroup).OrderBy("Name").ProjectTo<OrganizationViewModel>().ToListAsync();

以前有人运行关注过这个问题吗？看起来我正在尝试做一些不受支持的事情，这是设计使然吗？感谢任何 help/insight.

Answer 1

看起来问题是由 OrganizationViewModel class 的 OrganizationGroup 属性引起的 - AutoMapper 生成空检查，EF Core 不喜欢与您的 OrderBy 相结合（我想这只是目前 EF Core 中的众多错误之一）。它可以通过以下简单的手动投影查询轻松重现：

var tmp5a = _context.Organizations
    .OrderBy(x => x.OrganizationGroup.Name)
    .Select(e => new OrganizationViewModel
    {
        Id = e.Id,
        OrganizationGroup = e.OrganizationGroup != null ? new OrganizationGroupViewModel
        {
             Id = e.OrganizationGroup.Id,
             Name = e.OrganizationGroup.Name,
             Active = e.OrganizationGroup.Active,
        } : null,
    })
    .ToList();

要解决此问题，请将 AutoMapper 配置为不生成 null 检查属性，如下所示：

CreateMap<Organization, OrganizationViewModel>()
    .ForMember(dest => dest.OrganizationGroup, opt => opt.AllowNull())
    .ForMember(dest => dest.OrganizationGroupName, opt => opt.MapFrom(src => src.OrganizationGroup.Name));

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