带有 Linq OrderBy 子属性错误的 Automapper 投影

Question

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

"必须是可约节点"

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，我可以运行前 2 个语句并获得结果：

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，我得到了上面列出的错误：

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 Projections 对父类的属性进行 OrderBy，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();

以前有人遇到过这个问题吗？看起来我正在尝试做一些其他不支持的事情，这是设计使然吗？感谢您的帮助/见解。

Answer 1

看起来问题是由OrganizationViewModel 类的OrganizationGroup 属性引起的 - AutoMapper 生成一个空检查，EF Core 不喜欢与您的OrderBy 结合使用（我猜只是其中之一EF Core 中当前存在的错误）。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 检查该属性，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));