EF Core 多对多相同对象出错

Question

我的情况是我有一个包含发票的系统，我可以为每张发票创建收据。

这种关系是多对多的，因为我可以为每张发票生成几张收据，而且当我创建收据时，我可以将它与几张发票相关联。

我有以下两个类：代表发票或收据的Document，以及文件之间关联的DocumentOffset。

public class Document
{
    public Document()
    {
    }

    public int ID { get; set; }
    public string Reference { get; set; }
    [Required]
    public int? DocumentKind { get; set; }
    [Required]
    public long DocumentNum { get; set; }
    [Required]
    public DateTime? CreateDate { get; set; }
    [Required]
    public int? EntityID { get; set; }
    public double TaxDeduction { get; set; }
    public int Amount { get; set; }

    public double SumBeforeDiscount
    {
        get
        {
            return Document2List.Sum(x => x.Sum);
        }
    }

    public double DiscountPercent { get; set; }

    public double DiscountValue 
    { 
        get
        {
            return SumBeforeDiscount * DiscountPercent / 100;
        }
    }

    public double SumBeforeTax 
    {
        get
        {
            return SumBeforeDiscount - DiscountValue;
        }
    }

    public int TaxPercent { get; set; } = 17;
    public double TaxValue 
    {
        get
        {
            return SumBeforeTax * TaxPercent / 100;
        }
    }

    public double Sum 
    {
        get
        {
            if(DocumentKind == (int)Enums.DocumentKind.eDocumentKind.Reciept || DocumentKind == (int)Enums.DocumentKind.eDocumentKind.SupplierReciept)
            {
                return Document3List.Sum(x => x.Sum).Value;
            }

            return SumBeforeTax + TaxValue;
        }
    }

    public double Paid 
    {
        get
        {
            return Document3List.Where(x => x.Sum.HasValue).Sum(x => x.Sum.Value);
        }
    }

    public double Balance 
    {
        get
        {
            return Sum - Paid;
        }
    }

    [Required]
    public string Details { get; set; }
    [Required]
    public DateTime? Expire { get; set; }
    public string VehicleID { get; set; }

    public List<Document2> Document2List { get; set; } = new List<Document2>(); // Document items
    public List<Document3> Document3List { get; set; } = new List<Document3>(); // Document payments when invoice and receipt produced in the same document
    public Entity Entity { get; set; }

    public ICollection<DocumentOffset> DocumentOffsets { get; set; } //this property
}

和

public class DocumentOffset
{
    public int DocumentID { get; set; } //FK
    public Document Document { get; set; }
    public int RelatedDocumentID { get; set; } //FK
    public Document RelatedDocument { get; set; }
    public double Sum { get; set; }
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
        modelBuilder.Entity<MissionCardWorker>().HasKey(x => new { x.MissionCardId, x.WorkerId });
        modelBuilder.Entity<MissionCardItems>().HasKey(x => new { x.MissionCardId, x.ItemId });
        modelBuilder.Entity<MissionCardMission>().HasKey(x => new { x.MissionCardId, x.MissionId });

        modelBuilder.Entity<DocumentOffset>()
            .HasOne(x => x.Document)
            .WithMany(x => x.DocumentOffsets)
            .HasForeignKey(x => x.RelatedDocumentID);

        modelBuilder.Entity<DocumentOffset>()
            .HasOne(x => x.RelatedDocument)
            .WithMany(x => x.DocumentOffsets)
            .HasForeignKey(x => x.DocumentID);
 }

当我尝试添加迁移时出现以下错误：

Cannot create a relationship between 'Document.DocumentOffsets' and 'DocumentOffset.RelatedDocument', because there already is a relationship between 'Document.DocumentOffsets' and 'DocumentOffset.Document'. Navigation properties can only participate in a single relationship.

我应该怎么做才能解决这个问题？

谢谢:)

Answer 1

通常，对于多对多连接，您会遵循这样的模式；

public class Parent{
   public int Id { get; set; }
   public virtual ICollection<Join> Join { get; set; }
}
public class Join{
   public int ParentId { get; set; }
   public int ChildId { get; set; }
   public virtual Parent Parent { get; set; }
   public virtual Child Child { get; set; }

}
public class Child{
   public int Id { get; set; }
   public virtual ICollection<Join> Join { get; set; }
}

modelBuilder.Entity<Join>()
            .HasOne(x => x.Parent)
            .WithMany(x => x.Join)
            .HasForeignKey(x => x.ParentId);

modelBuilder.Entity<Join>()
            .HasOne(x => x.Child)
            .WithMany(x => x.Join)
            .HasForeignKey(x => x.ChildId);

但在您的情况下，您正试图将 Parent 和 Child 合并为同一类型。您仍然需要相同数量的外键和导航属性，但当然它们都需要是唯一的。

public class Document{
   public int Id { get; set; }
   public virtual ICollection<DocumentOffset> Parents { get; set; }
   public virtual ICollection<DocumentOffset> Children { get; set; }
}
public class DocumentOffset{
   public int ParentId { get; set; }
   public int ChildId { get; set; }
   public virtual Document Parent { get; set; }
   public virtual Document Child { get; set; }
}

modelBuilder.Entity<DocumentOffset>()
            .HasOne(x => x.Parent)
            .WithMany(x => x.Children)
            .HasForeignKey(x => x.ParentId);

modelBuilder.Entity<DocumentOffset>()
            .HasOne(x => x.Child)
            .WithMany(x => x.Parents)
            .HasForeignKey(x => x.ChildId);

EF Core 多对多相同对象出错

EF Core many to many of same object get error

c#

sql

entity-framework

ef-code-first

entity-framework-core