EF Core 循环关系映射

Question

给定以下实体模型：

public class Workshop
{
    public Guid Id { get; set; }
    public string Name { get; set; }

    public ICollection<QuoteRequest> QuoteRequests { get; set; }
}

public class QuoteRequest
{
    public Guid Id { get; set; }
    public Guid CustomerId { get; set; }
    public Guid WorkshopId { get; set; }
    public bool Responded { get; set; }
    public decimal? Amount { get; set; }

    public virtual Customer Customer { get; set; }
    public virtual Workshop Workshop { get; set; }
}

以及以下 2 个视图模型：

public class WorkshopModel
{
    public Guid Id { get; set; }
    public string Name { get; set; }

    public ICollection<QuoteRequestModel> QuoteRequests { get; set; }
}

public class QuoteRequestModel
{
    public Guid Id { get; set; }
    public Guid CustomerId { get; set; }
    public Guid WorkshopId { get; set; }
    public bool Responded { get; set; }
    public decimal? Amount { get; set; }

    public CustomerModel Customer { get; set; }
    public WorkshopModel Workshop { get; set; }
}

接下来，给出以下查询：

    public async Task<Workshop> GetWorkshopAsync(Guid id, bool includeQuotes = false)
    {
        IQueryable<Workshop> query = _context.Workshops;

        if (includeQuotes)
        {
            query = query.Include(w => w.QuoteRequests);
        }

        return await query.FirstOrDefaultAsync(w => w.Id == id);
    }

无论我做什么，我都无法让 EF 在查询 Workshop 时不给我循环关系。比如我查询一个Workshop有14个QuoteRequests，每个有一个Workshop，每个有14个QuoteRequests等等等等：

我确实将 json 序列化程序引用循环处理设置设置为忽略，但这并没有给我想要的结果

services.AddControllers()
        .AddNewtonsoftJson(x => x.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore);

我想在我的映射配置文件中删除这个圆圈。我正在使用自动映射器。我已经设法从 QuoteRequest 端用我的映射配置文件打破循环引用：

CreateMap<QuoteRequestModel, QuoteRequest>()
    .ForMember(dest => dest.Customer, opt => opt.MapFrom(src => src.Customer))
    .ForMember(dest => dest.Workshop, opt => opt.MapFrom(src => src.Workshop))
    .ForPath(dest => dest.Customer.QuoteRequests, opt => opt.MapFrom(src => new List<QuoteRequest>()))
    .ForPath(dest => dest.Workshop.QuoteRequests, opt => opt.MapFrom(src => new List<QuoteRequest>()));

CreateMap<QuoteRequest, QuoteRequestModel>()
    .ForMember(dest => dest.Customer, opt => opt.MapFrom(src => src.Customer))
    .ForMember(dest => dest.Workshop, opt => opt.MapFrom(src => src.Workshop))
    .ForPath(dest => dest.Customer.QuoteRequests, opt => opt.MapFrom(src => new List<QuoteRequestModel>()))
    .ForPath(dest => dest.Workshop.QuoteRequests, opt => opt.MapFrom(src => new List<QuoteRequestModel>()));

这可能是一个有点卡顿的解决方案，但现在当我查询个人 QuoteRequest 时它可以正常工作。我想弄清楚的是如何在 Workshop 端的映射配置文件中执行相同的操作：

CreateMap<WorkshopModel, Workshop>()
    .ForMember(dest => dest.QuoteRequests, opt => opt.MapFrom(src => src.QuoteRequests));

CreateMap<Workshop, WorkshopModel>()
    .ForMember(dest => dest.QuoteRequests, opt => opt.MapFrom(src => src.QuoteRequests));

我无法真正针对 QuoteRequests 的每次迭代设置 Workshop 默认值。

Answer 1

这不是问题。您看到的是 EF 的对象修复。因为它的对象缓存中已经有这些实体，所以它会自动 "fixes up" 每个实体的关系，而无需再次查询任何内容。

唯一一次这可能是序列化期间的问题，因为序列化将尝试无限期地递归向下钻取。然而，根据序列化方法的不同，有不同的方法来防止这种递归序列化。此外，无论如何，您真的不应该直接序列化实体。相反，您应该将它们映射到 DTO 类，然后您可以在其中定义一个不会遇到相同递归问题的更基本的结构。然后，您将序列化 DTO，而不是实体。

EF Core 循环关系映射

EF Core Circular Relationship Mapping

entity-framework

automapper

entity-framework-core

asp.net-core