Question

我对EF很新，我有一点问题。

我只想删除数据库中的项目。我正在使用SQL Server 2012 Express，VS2012，AdventureWorks 2012.

我执行的查询如下：

context = new AWEntities();
            var removedItem = context.Addresses
                .Include("StateProvince")
                .Include("SalesOrderHeaders")
                .Include("BusinessEntityAddresses").Single(d => d.AddressID == 11);
            context.Addresses.Remove(removedItem);

context.SaveChanges();

我得到的错误是

DELETE语句与REFERENCE约束“FK_SalesOrderHeader_Address_ShipToAddressID”冲突。冲突发生在数据库“AdventureWorks2012”，表“Sales.SalesOrderHeader”，列“ShipToAddressID”中。声明已经终止。

这实际上是删除其他表中的项目和相应条目的好方法吗？

请指出我正确的方向。

   public partial class Address
    {
        public Address()
        {
            this.BusinessEntityAddresses = new HashSet<BusinessEntityAddress>();
            this.SalesOrderHeaders = new HashSet<SalesOrderHeader>();
        }

        public int AddressID { get; set; }
        public string AddressLine1 { get; set; }
        public string AddressLine2 { get; set; }
        public string City { get; set; }
        public int StateProvinceID { get; set; }
        public string PostalCode { get; set; }
        public System.Data.Spatial.DbGeography SpatialLocation { get; set; }
        public System.Guid rowguid { get; set; }
        public System.DateTime ModifiedDate { get; set; }

        public virtual StateProvince StateProvince { get; set; }
        public virtual ICollection<BusinessEntityAddress> BusinessEntityAddresses { get; set; }
        public virtual ICollection<SalesOrderHeader> SalesOrderHeaders { get; set; }
    }


public partial class StateProvince
    {
        public StateProvince()
        {
            this.Addresses = new HashSet<Address>();
            this.SalesTaxRates = new HashSet<SalesTaxRate>();
        }

        public int StateProvinceID { get; set; }
        public string StateProvinceCode { get; set; }
        public string CountryRegionCode { get; set; }
        public bool IsOnlyStateProvinceFlag { get; set; }
        public string Name { get; set; }
        public int TerritoryID { get; set; }
        public System.Guid rowguid { get; set; }
        public System.DateTime ModifiedDate { get; set; }

        public virtual ICollection<Address> Addresses { get; set; }
        public virtual CountryRegion CountryRegion { get; set; }
        public virtual ICollection<SalesTaxRate> SalesTaxRates { get; set; }
        public virtual SalesTerritory SalesTerritory { get; set; }
    }
}

public partial class BusinessEntityAddress
{
    public int BusinessEntityID { get; set; }
    public int AddressID { get; set; }
    public int AddressTypeID { get; set; }
    public System.Guid rowguid { get; set; }
    public System.DateTime ModifiedDate { get; set; }

    public virtual Address Address { get; set; }
    public virtual AddressType AddressType { get; set; }
    public virtual BusinessEntity BusinessEntity { get; set; }
}


public partial class SalesOrderHeader
    {
        public SalesOrderHeader()
        {
            this.SalesOrderDetails = new HashSet<SalesOrderDetail>();
            this.SalesOrderHeaderSalesReasons = new HashSet<SalesOrderHeaderSalesReason>();
        }

        public int SalesOrderID { get; set; }
        public byte RevisionNumber { get; set; }
        public System.DateTime OrderDate { get; set; }
        public System.DateTime DueDate { get; set; }
        public Nullable<System.DateTime> ShipDate { get; set; }
        public byte Status { get; set; }
        public bool OnlineOrderFlag { get; set; }
        public string SalesOrderNumber { get; set; }
        public string PurchaseOrderNumber { get; set; }
        public string AccountNumber { get; set; }
        public int CustomerID { get; set; }
        public Nullable<int> SalesPersonID { get; set; }
        public Nullable<int> TerritoryID { get; set; }
        public int BillToAddressID { get; set; }
        public int ShipToAddressID { get; set; }
        public int ShipMethodID { get; set; }
        public Nullable<int> CreditCardID { get; set; }
        public string CreditCardApprovalCode { get; set; }
        public Nullable<int> CurrencyRateID { get; set; }
        public decimal SubTotal { get; set; }
        public decimal TaxAmt { get; set; }
        public decimal Freight { get; set; }
        public decimal TotalDue { get; set; }
        public string Comment { get; set; }
        public System.Guid rowguid { get; set; }
        public System.DateTime ModifiedDate { get; set; }

        public virtual Address Address { get; set; }
        public virtual ShipMethod ShipMethod { get; set; }
        public virtual CreditCard CreditCard { get; set; }
        public virtual CurrencyRate CurrencyRate { get; set; }
        public virtual Customer Customer { get; set; }
        public virtual ICollection<SalesOrderDetail> SalesOrderDetails { get; set; }
        public virtual SalesPerson SalesPerson { get; set; }
        public virtual SalesTerritory SalesTerritory { get; set; }
        public virtual ICollection<SalesOrderHeaderSalesReason> SalesOrderHeaderSalesReasons { get; set; }
    }

Answer 1

无法从你所说的内容中说出多少，但是你可以从使用DbModelBuilder解决级联问题中受益：

            modelBuilder.Entity<Parent>()
                .HasMany<Child>(c => c.Children)
                .WithOptional(x => x.Parent)
                .WillCascadeOnDelete(true);

同样，需要有关模型结构的更多信息，以确定这是否是正确的方法。

要么在删除方法中，要先删除所有子节点，然后删除父节点。

Answer 2

  modelBuilder.Entity<Parent>()
  .HasMany<Child>(c => c.Children)
  .WithOptional(x => x.Parent)
  .WillCascadeOnDelete(true);

或使用Include

  var adv = db.Adv.Include(b => b.Features)
                  .Include(b => b.AdvDetails)
                  .Include(b => b.AdvGallery)
                  .FirstOrDefault(b => b.Id == id);
  db.Adv.Remove(adv);

for .HasMany（...）。WithMany（...）Include is ok

Answer 3

您可以在SQL端解决此问题

方法1 ：

首先，您需要使用FK找到已定义此Replication monitor约束的表格。
右键点击FK，点击Modify，您会看到如下所示的弹出框。

在弹出框中，为Cascade选择del。

方法2 ：

在约束结束时在sql中设置ON DELETE CASCADE。

Answer 4

在EF Core中，构建器中的语法如下：

builder.HasOne(b => b.Parent )
  .WithMany(a => a.Children)
  .OnDelete(DeleteBehavior.Cascade);

https://docs.microsoft.com/en-us/ef/core/saving/cascade-delete

Answer 5

创建实体B（引用实体A）然后尝试删除实体A时遇到此错误。SQL/ EF不允许我离开那个悬空的ID引用，因为objcet不再存在。级联删除可以解决此问题，但我希望B继续存在。所以我必须先删除B的引用，然后再删除A：

    var existingContractApprovers = _repo.Query<ChangeOrderApproverForContract>().Where(coafc => coafc.ContractId == key).ToList();
    //remove refs to contract approvers to preserve data integrity
    foreach(var contractApp in existingContractApprovers)
    {
        var associatedChangeOrderApprovers = _repo.Query<ChangeOrderApprover>().AsNoTracking().Where(coafc => coafc.ChangeOrderApproverForContractId == contractApp.Id).ToList();
        foreach(var coApp in associatedChangeOrderApprovers)
    {
            _repo.Edit(coApp);
            coApp.ChangeOrderApproverForContractId = null;
        }
    }
    _repo.SaveChanges();

    //remove the contract approvers
    foreach (var contractApp in existingContractApprovers)
    {
        _repo.Delete(contractApp);
    }
    _repo.SaveChanges();

Answer 6

您可以在EF Core中执行此操作。

modelBuilder.Entity<Parent>()
    .HasMany<Child>(c => c.Children)
    .WithOne(s => s.Parent)
    .OnDelete(DeleteBehavior.Cascade);

更安全的选择是确保在删除父级之前删除所有子级。仅当您完全了解实体之间的关系时，才应在Delete上级联。例如，您可能有很多订单连接到您的电子商务商店中的某个类别。删除类别后，所有订单以及与该父类别相关联的外键都将消失。

实体框架DELETE语句与REFERENCE约束冲突

6 个答案: