如果我尝试删除一个“子”行,我总是会得到一个异常。以下是代码片段:
以下异常会在
我找到了这篇博客,但我没有看到 "DeleteObject" 方法。
可以参考以下链接:http://blog.clicdata.com/2013/07/04/the-operation-failed-the-relationship-could-not-be-changed-because-one-or-more-of-the-foreign-key-properties-is-non-nullable/ 有什么建议吗?谢谢。
using (var context = new CompanyContext())
{
ItemType itemType = context.ItemTypes.FirstOrDefault(i => i.Name == "ServerType");
ItemTypeItem itemTypeItem = itemType.Items.FirstOrDefault(i => i.Name == "DatabaseServer");
itemType.Items.Remove(itemTypeItem);
context.SaveChanges(); <=== exception!
}
以下异常会在
SaveChanges()
方法中抛出。
实体配置“由于一个或多个外键属性是非空的,因此无法更改关系。当关系发生变化时,相关的外键属性被设置为null值。如果外键不支持null值,则必须定义新的关系,将外键属性分配给另一个非null值,或删除无关对象。”
public class ItemTypeConfiguration : NamedEntityConfiguration<ItemType>
{
public ConfigurationColumn ParentIDColumn;
public ConfigurationColumn ValidationPatternColumn;
public ItemTypeConfiguration() : base()
{
ParentIDColumn = new ConfigurationColumn() { Name = "ParentID", Ordinal = base.LastOrdinalPosition + 1 };
ValidationPatternColumn = new ConfigurationColumn() { Name = "ValidationPattern", Length = 1024, Ordinal=base.LastOrdinalPosition + 2};
this.Property(t => t.ParentID)
.HasColumnName(ParentIDColumn.Name)
.HasColumnOrder(ParentIDColumn.Ordinal);
this.HasOptional(t => t.Parent).WithMany().HasForeignKey(u => u.ParentID).WillCascadeOnDelete(false);
this.Property(t => t.ValidationPattern)
.HasColumnName(ValidationPatternColumn.Name)
.HasColumnOrder(ValidationPatternColumn.Ordinal)
.HasMaxLength(ValidationPatternColumn.Length);
}
...
public class ItemTypeItemConfiguration : NamedEntityConfiguration<ItemTypeItem>
{
public ConfigurationColumn ItemTypeIDColumn;
public ItemTypeItemConfiguration() : base()
{
ItemTypeIDColumn = new ConfigurationColumn(){Name="ItemTypeID", IsRequired=true, Ordinal= base.LastOrdinalPosition+1};
this.Property(t => t.ItemTypeID)
.HasColumnName(ItemTypeIDColumn.Name)
.HasColumnOrder(ItemTypeIDColumn.Ordinal);
this.HasRequired(t => t.ItemType).WithMany(t=>t.Items).HasForeignKey(u => u.ItemTypeID).WillCascadeOnDelete(true);
}
...
我找到了这篇博客,但我没有看到 "DeleteObject" 方法。
可以参考以下链接:http://blog.clicdata.com/2013/07/04/the-operation-failed-the-relationship-could-not-be-changed-because-one-or-more-of-the-foreign-key-properties-is-non-nullable/ 有什么建议吗?谢谢。