Question

实体模型：

public class DocumentType : CodeBase
{
    [Required]
    [MaxLength(100)]
    public string Name { get; set; }

    public TimeSpan? Productiontime { get; set; }

    public bool IsDeliverable { get; set; }

    public virtual ICollection<DocumentTypeRetractRelation> DocumentTypes { get; set; }
    public virtual ICollection<DocumentTypeRetractRelation> RetractDocumentTypes { get; set; }
}

关系模型：

/// <summary>
/// Relationship between document types showing which documenttypes can 
/// retracted when delivering a new document.
/// </summary>
[Table("DocumentTypeRetractRelation")]
public class DocumentTypeRetractRelation
{
    public int DocumentTypeId { get; set; }
    public virtual DocumentType DocumentType { get; set; }

    public int RetractDocumentTypeId { get; set; }
    public virtual DocumentType RetractDocumentType { get; set; }
}

模型构建器：

modelBuilder.Entity<DocumentTypeRetractRelation>().HasKey(x => new { x.DocumentTypeId, x.RetractDocumentTypeId });

modelBuilder.Entity<DocumentTypeRetractRelation>()
    .HasOne(x => x.DocumentType)
    .WithMany(x => x.DocumentTypes)
    .HasForeignKey(x => x.DocumentTypeId);

modelBuilder.Entity<DocumentTypeRetractRelation>()
    .HasOne(x => x.RetractDocumentType)
    .WithMany(x => x.RetractDocumentTypes)
    .HasForeignKey(x => x.RetractDocumentTypeId);

更新作家：

    public async Task<DocumentType> UpdateAsync(DocumentTypeUpdateDto documentTypeUpdateDto)
    {
        using (IUnitOfWork uow = UowProvider.CreateUnitOfWork<EntityContext>())
        {
            var documentTypeRepo = uow.GetCustomRepository<IDocumentTypeRepository>();

            var existingDocument = await documentTypeRepo.GetAsync(documentTypeUpdateDto.Id);

            if (existingDocument == null)
                throw new EntityNotFoundException("DocumentType", existingDocument.Id);

            foreach (var retractDocumentTypeId in documentTypeUpdateDto.RetractDocumentTypeIds)
            {
                existingDocument.RetractDocumentTypes.Add(new DocumentTypeRetractRelation()
                {
                    DocumentTypeId = existingDocument.Id,
                    RetractDocumentTypeId = retractDocumentTypeId
                });
            }

            documentTypeRepo.Update(existingDocument);

            await uow.SaveChangesAsync();

            return existingDocument;
        }
    }

尝试更新existingDocument时，出现以下错误：

实体类型'DocumentTypeRetractRelation'的实例不能跟踪，因为具有相同密钥的此类型的另一个实例是已被跟踪。添加新实体时，对于大多数关键类型a 如果没有设置密钥，则将创建唯一的临时密钥值（即，如果 key属性被赋予其类型的默认值）。如果你明确设置新实体的关键值，确保不这样做与现有实体或为其他实体生成的临时值发生冲突新实体。附加现有实体时，请确保只有一个实体具有给定键值的实体实例附加到上下文。

Answer 1

问题不在于自引用，而是应用多对多的集合修改，这些修改生成具有与异常消息中所述相同的PK的不同DocumentTypeRetractRelation个对象。

EF Core中当前的正确方法是确保加载RetractDocumentTypes existingDocument（包含原始值），然后使用现有合并或创建新{{1}合并更改对象。

替换以下代码

DocumentTypeRetractRelation

与

foreach (var retractDocumentTypeId in documentTypeUpdateDto.RetractDocumentTypeIds)
{
    existingDocument.RetractDocumentTypes.Add(new DocumentTypeRetractRelation()
    {
        DocumentTypeId = existingDocument.Id,
        RetractDocumentTypeId = retractDocumentTypeId
    });
}

这将处理添加，删除和未更改的关系。您可以执行与// existingDocument.RetractDocumentTypes should be loaded (either eager or explicit) existingDocument.RetractDocumentTypes = ( from retractDocumentTypeId in documentTypeUpdateDto.RetractDocumentTypeIds join existingRelation in existingDocument.RetractDocumentTypes on retractDocumentTypeId equals existingRelation.RetractDocumentTypeId into existingRelations select existingRelations.FirstOrDefault() ?? new DocumentTypeRetractRelation() { DocumentTypeId = existingDocument.Id, RetractDocumentTypeId = retractDocumentTypeId }).ToList();类似的操作。

实际上看一下你的模型，上面的代码应该是DocumentTypes集合（因为你收到了DocumentTypes，它与文档RetractDocumentTypeIds结合形成Id收集内容）。因此，只需将DocumentTypes替换为RetractDocumentTypes。

EF核心 - 自我引用多对多关系

1 个答案: