[英]Entity Framework one-to-many and many-to-many relationship
即時通訊目前正在學習實體框架,並且在幾天內完成了這項任務的失敗...我希望實現以下數據庫方案:
TableA:
ClassA_ID
ClassB_ID(foreign key - one to one)
TableATableB:(one-to-many relationship)
ClassA_ID
ClassB_ID
TableB:
ClassA_ID(foreign key - one to one)
ClassB_ID
所以我實際上想要從A類到B類的特定的一對一關系以及從ClassA到ClassB的一對多關系。
我的C#代碼看起來像這樣:
A類:
public static int idcounter;
[Key]
public int id { get; set; }
public virtual List<ClassB> allClassB { get; set; }
public virtual ClassB currentClassB { get; set; }
public int? currentClassBID { get; set; }
public ClassA(){
idcounter++;
id = idcounter;
allClassB = new List<ClassB>();
currentClassB = new ClassB();
currentClassBID = currentClassB.id;
MyContext.add(this);
}
B級:
public static int idcounter;
[Key]
public int id { get; set; }
public virtual ClassA owner { get; set; }
public int? ownerID { get; set; }
public ClassB(ClassA a){
idcounter++;
id = idcounter;
owner = a;
ownerID = a.id;
}
MyContext:
public static void add(ClassA a)
{
using (MyContext context = new MyContext ())
{
context.setB.Add(a.currentClassB);
context.setA.Add(a);
context.SaveChanges();
}
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<ClassA>().HasOptional(x => x.currentClassB ).WithMany().HasForeignKey(x => x.currentClassBID ).WillCascadeOnDelete(false);
modelBuilder.Entity<ClassB>().HasOptional(x => x.ClassA).WithMany(x => x.allClassB).HasForeignKey(x => x.ownerID).WillCascadeOnDelete(false) ;
}
它非常類似於這個問題實體框架代碼第一:如何在兩個表之間創建一對多和一對一的關系? 但是我在保存時只收到循環異常。
Unable to determine a valid ordering for dependent operations. Dependencies may
exist due to foreign key constraints, model requirements, or store-generated
values.
之后非常奇怪
context.setA.Add(a);
它將currentClassB添加到allClassB中,而我沒有提到過......它甚至在我不這樣做時突然做到了
allClassB = new List<ClassB>();
我究竟做錯了什么?
您必須使用InverseProperty
,如下所示。
[InverseProperty("allClassB")]
public virtual ClassB currentClassB { get; set; }
public int? currentClassBID { get; set; }
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