外鍵沖突

Question

// EDMX文件http://pastebin.com/btTCRMf7

我有2張桌子Customers和Sites

//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);

我越來越A referential integrity constraint violation occurred: The property values that define the referential constraints are not consistent between principal and dependent objects in the relationship.

但是，添加test.Customer.City = null; 在更新對象之前，它將起作用。 似乎Customer.City和Site.City發生沖突。 有人可以解釋為什么嗎？ 或任何解決方法？

Answer 1

我可以解釋為什么。 Includepersistentity實體用於加載所有include對象。因此，我們的站點對象具有對您的線索的所有引用（城市，國家/地區，用戶客戶）。 我認為這就是問題所在。 解決方法是僅加載站點對象：

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

因此它將僅加載站點對象的ID。 比您可以在需要的運行時中通過其ID加載引用的對象。

我認為這是因為使用include時，您會操作對象和對象集合dbContext會跟蹤此更改並在您調用時保存它們

context.SaveChanges();

一點重構的代碼順便說一句：

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
    }
  }

評論答案 Slauma如果我不將其設置為null，我將無法在更新方法中附加它們，則將觸發相同的錯誤

答：因為當包含所有實體時，您已經附加到上下文對象。 Btw在sql內部連接語句上包含轉換，因此可能是您的db對象快照不包含具有該ID的City。