ef核心同一对象的多对多get错误

我的情况是，我有一个系统，其中包含发票和每张发票，我可以创建一个收据。
这种关系是多对多的，因为我可以为每个发票生成几个收据，而且当我创建收据时，我可以将它与几个发票关联起来。
我有以下两门课： Document 代表发票或收据，以及 DocumentOffset 文件之间的关联。

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);
 }

尝试添加迁移时，出现以下错误：
无法在“document.documentoffset”和“documentoffset.relateddocument”之间创建关系，因为“document.documentoffset”和“documentoffset.document”之间已经存在关系。导航属性只能参与单个关系。
我该怎么办？
谢谢：）

通常，对于多对多的加入，你会遵循这样的模式；

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);

但你想合并 Parent 以及 Child 变成同一类型。您仍然需要相同数量的外键和导航属性，但它们当然都需要是唯一的。

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核心同一对象的多对多get错误

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