现在,在某些触发器中,有必要检测某些关系是否已经改变,无论多对多,一对一/零等.
我已经阅读了互联网上的一些帖子,包括本网站上的一些帖子,提到DbContext API没有公开任何获取关系信息的方法.
但是,ObjectContext应该能够.
我的SaveChanges方法:
public overrIDe int SaveChanges(){ IEntity entity; ChangeTracker.DetectChanges(); var stateManager = ((IObjectContextAdapter)this).ObjectContext.ObjectStateManager; var added = stateManager.GetobjectStateEntrIEs(EntityState.Added).ToList(); var updated = stateManager.GetobjectStateEntrIEs(EntityState.ModifIEd).ToList(); var deleted = stateManager.GetobjectStateEntrIEs(EntityState.Deleted).ToList(); var unchanged = stateManager.GetobjectStateEntrIEs(EntityState.Unchanged).ToList(); while ((entity = _entitIEsRequiringTriggering.FirstOrDefault(x => x.Value).Key) != null) { _entitIEsRequiringTriggering[entity] = false; var entry = ChangeTracker.EntrIEs<IEntity>().SingleOrDefault(x => x.State != EntityState.Unchanged && x.Entity == entity); if (entry == null) continue; var trigger = Triggers.Triggers.GetTriggerForEntity(entry.Entity,this); if (trigger == null) continue; trigger.BeforeSave(entry.Entity); switch (entry.State) { case EntityState.Added: trigger.BeforeAdd(entry.Entity); break; case EntityState.ModifIEd: trigger.BeforeUpdate(entry.Entity); break; case EntityState.Deleted: trigger.BeforeDelete(entry.Entity); break; } } return base.SaveChanges();}
请注意添加,更新,删除和更改的四个变量.
根据我到目前为止所发现的,GetobjectStateEntrIEs应该返回ObjectStateEntry的集合,该集合具有IsRelationship属性.
我在测试应用程序中运行以下代码:
using (var db = container.Resolve<IDatabaseContext>()){ var cus = db.query<Customer>().Single(x => x.ID == 1); var newAddress = db.query<Address>().Single(x => x.ID == 5); cus.Address = newAddress; //also sets the foreign key property Customer.AddressID to its new corresponding value db.SaveChanges();}
当我在调用后检查SaveChanges中的代码时,我得到了预期的结果:
一个结果在更新列表中,Customer对象.
但在任何时候,我都没有获得关系(一对一)Customer_Address的ObjectStateEntry.
我需要能够在关系发生变化时如前所述进行检测.
对于正常的标量属性,您可以这样做:
var changed = DbEntry.Property(x => x.name).OriginalValue == DbEntry.Property(x => x.name).CurrentValue;
但对于不明显起作用的参考属性.
有任何想法吗?
public static class DbContextExtensions{ public static IEnumerable<Tuple<object,object>> GetRelationships( this DbContext context) { return GetAddedRelationships(context) .Union(GetDeletedRelationships(context)); } public static IEnumerable<Tuple<object,object>> GetAddedRelationships( this DbContext context) { return GetRelationships(context,EntityState.Added,(e,i) => e.CurrentValues[i]); } public static IEnumerable<Tuple<object,object>> GetDeletedRelationships( this DbContext context) { return GetRelationships(context,EntityState.Deleted,i) => e.OriginalValues[i]); } private static IEnumerable<Tuple<object,object>> GetRelationships( this DbContext context,EntityState relationshipState,Func<ObjectStateEntry,int,object> getValue) { context.ChangeTracker.DetectChanges(); var objectContext = ((IObjectContextAdapter)context).ObjectContext; return objectContext.ObjectStateManager .GetobjectStateEntrIEs(relationshipState) .Where(e => e.IsRelationship) .Select( e => Tuple.Create( objectContext.GetobjectByKey((EntityKey)getValue(e,0)),objectContext.GetobjectByKey((EntityKey)getValue(e,1)))); }}总结
以上是内存溢出为你收集整理的c# – 实体框架6:检测关系变化全部内容,希望文章能够帮你解决c# – 实体框架6:检测关系变化所遇到的程序开发问题。
如果觉得内存溢出网站内容还不错,欢迎将内存溢出网站推荐给程序员好友。
欢迎分享,转载请注明来源:内存溢出
评论列表(0条)