c# – 外键冲突

2019年7月21日 201次阅读

// EDMX文件

http://pastebin.com/btTCRMf7

我有2个表客户和网站

//Site
public int ID { get; set; }
public string Name { get; set; }
public string Address { get; set; }
public int CustomerID { get; set; }
public int CityID { get; set; }
public int CountryID { get; set; }
public int EncodedBy { get; set; }
public System.DateTime DateEncoded { get; set; }

public virtual City City { get; set; }
public virtual Country Country { get; set; }
public virtual ICollection<Invoice> Invoices { get; set; }
public virtual User User { get; set; }
public virtual Customer Customer { get; set; }

//Customer
public int ID { get; set; }
public string Name { get; set; }
public string Address { get; set; }
public int CityID { get; set; }
public int CountryID { get; set; }
public int CreditTermID { get; set; }
public int EncodedBy { get; set; }
public System.DateTime DateEncoded { get; set; }
public virtual City City { get; set; }
public virtual Country Country { get; set; }
public virtual CreditTerm CreditTerm { get; set; }
public virtual User User { get; set; }
public virtual ICollection<Invoice> Invoices { get; set; }
public virtual ICollection<Site> Sites { get; set; }

//Country
public int ID { get; set; }
public string Name { get; set; }
public virtual ICollection<Customer> Customers { get; set; }
public virtual ICollection<Site> Sites { get; set; }

//City
public int ID { get; set; }
public string Name { get; set; }

public virtual ICollection<Customer> Customers { get; set; }
public virtual ICollection<Site> Sites { get; set; }


//SiteModel
private static IQueryable<Site> Build(this DbSet<Site> query)
{
    return query.Include("User").Include("City").Include("Country").Include("Customer");
}

public static Site Find(int siteID)
{
    using (DragonRentalsEntities context = new DragonRentalsEntities(new ConfigurationManager().ConnectionString))
    {
        Site result = context.Sites.Build().SingleOrDefault(s => s.ID == siteID);
        return result;
    }
}

public static Site Update(Site _updatedSite)
{
    using (DragonRentalsEntities context = new DragonRentalsEntities(new ConfigurationManager().ConnectionString))
    {
        context.Sites.Attach(_updatedSite);
        context.Entry(_updatedSite).State = EntityState.Modified;
        context.SaveChanges();
        return Find(_updatedSite.ID);
    }
}

Site test = SiteModel.Find(1);
test.City = null;
test.CityID = 1;
test.Country = null;
test.CountryID = 1;

test.Customer = null;
test.CustomerID = 1;

SiteModel.Update(test);

我发现了一个引用完整性约束违规：定义引用约束的属性值在关系中的主体和依赖对象之间不一致.

但是,添加test.Customer.City = null;在更新对象之前会起作用.似乎Customer.City和Site.City是冲突的.谁能解释一下为什么？或任何解决方法？

最佳答案 我可以解释一下原因.包括持久化实体以加载所有包含对象.因此,我们的站点对象具有对您的群集(城市,国家/地区,用户客户)的所有引用.我认为这就是问题所在.解决方法可以是只加载站点对象：

Site result = context.Sites.SingleOrDefault(s => s.ID == siteID);

所以它只加载站点对象的id.您可以在运行时根据需要加载引用的对象.

我认为这是因为当您使用include时,您操作对象和对象集合dbContext跟踪此更改并在您调用时保存它们

context.SaveChanges();

一点点重构代码顺便说一句：

public static Site Update(Site _updatedSite)
  {
     using (DragonRentalsEntities context = new DragonRentalsEntities(new ConfigurationManager().ConnectionString))
     {

          if (context.Entry(_updatedSite).State == EntityState.Detached)
               context.Entry(_updatedSite).State = EntityState.Modified;// attaches  entity and marks it as modified if it is detached

          context.SaveChanges();
          return _updatedSite; //after save changes u have the same object as u send in your Update function
    }
  }

评论答案
Slauma如果我没有将它设置为null,我将无法在更新方法中附加它们,同样的错误将被触发

回答：
因为当您包含已附加到上下文对象的所有实体时.
Btw Include转换sql内部连接语句,因此您的db对象的快照可能不包含具有该ID的City.

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