周期性参考问题？

本文介绍了周期性参考问题？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

每个练习都有一个与之相关的人。

Each Excercise has a person associated with it.

每个练习都有一系列与之相关的参与。

Each Excercise has a Collection of Engagements associated with it.

每个参与有2人关联它。我需要帮助Rowan。

Each Engagement has 2 people associated with it. I need help Rowan.

当我使用RelatedTo属性修饰SurveyPerson时，我得到了这个错误。

I am gettting this error when I decorate the SurveyPerson with a RelatedTo attribute.

参考关系将导致周期性不允许的引用。 [约束名称= Excercise_SurveyPerson]

The referential relationship will result in a cyclical reference that is not allowed. [ Constraint name = Excercise_SurveyPerson ]

namespaceTPS.KLE.Data{publicclassKLE_DB:DbContext{publicDbSet<Person>People{get;set;}publicDbSet<Excercise>Excercises{get;set;}publicDbSet<Engagement>Engagements{get;set;}} publicclassExcercise{publicintID{get;set;}publicstringName{get;set;}publicintInitalSiteSurveyPesonID{get;set;} publicvirtualICollection<Engagement>Engagements{get;set;} //thisattributecausesthecyclicalreferenceerror//withouttheattribute,SurveyPersonisnull[RelatedTo(ForeignKey="InitalSiteSurveyPesonID")]publicvirtualPersonSurveyPerson{get;set;}}publicclassEngagement{ publicintID{get;set;}publicintExcerciseID{get;set;}publicintOwnerID{get;set;}publicintTargetID{get;set;} publicvirtualExcerciseExcercise{get;set;}publicvirtualPersonOwner{get;set;}publicvirtualPersonTarget{get;set;}}publicclassPerson{publicintID{get;set;}publicstringFname{get;set;}publicstringLname{get;set;} publicvirtualICollection<Engagement>Engagements{get;set;}}}

推荐答案

Hi Te rrence，

Hi Terrence,

问题是Code First默认配置所需关系的级联删除。在您的情况下，删除参与将导致通过参与级联删除人员 - >人与参与 - >练习 - > Person，SQL Server 不支持此功能。

The issue is that Code First configures cascade delete on required relationships by default. In your case deleting an Engagement would cause a cascade delete of Person through Engagement -> Person and Engagement -> Exercise -> Person, SQL Server does not support this.

您需要关闭其中一个级联删除，这里有一些Fluent API代码可以关闭练习 - >人级联删除;

You need to switch off one of the cascade deletes, here is some Fluent API code to switch off the Exercise -> Person cascade delete;

protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<Excercise>() .HasRequired(e => e.SurveyPerson) .WithMany() .HasConstraint((e, p) => e.InitalSiteSurveyPesonID == p.ID) .WillCascadeOnDelete(false); }

~Rowan