c# – 实体框架 – 保存对分离状态下相关对象的更改
发布时间:2020-12-15 07:56:26 所属栏目:百科 来源:网络整理
导读:我正在使用Northwind数据库作为此帖的示例,我在使用实体框架将分离的实体保存回数据库时遇到问题. 我有以下两种方法来获取区域和区域: static ListRegion GetRegions() { using (NorthwindEntities entities = new NorthwindEntities()) { entities.Region.
我正在使用Northwind数据库作为此帖的示例,我在使用实体框架将分离的实体保存回数据库时遇到问题.
我有以下两种方法来获取区域和区域: static List<Region> GetRegions() { using (NorthwindEntities entities = new NorthwindEntities()) { entities.Region.MergeOption = System.Data.Objects.MergeOption.NoTracking; return entities.Region.ToList(); } } static List<Territories> GetTerritories() { using (NorthwindEntities entities = new NorthwindEntities()) { entities.Territories.MergeOption = System.Data.Objects.MergeOption.NoTracking; return entities.Territories.ToList(); } } 这些方法都可以正常工作,并让我在分离状态下获得所需的对象集合. 我还有一个名为SaveEntity的静态方法,它接受旧实体和当前编辑的实体,如下所示: static void SaveEntity(EntityObject oldEntity,EntityObject newEntity) { using (NorthwindEntities entities = new NorthwindEntities()) { entities.Attach(oldEntity); entities.ApplyPropertyChanges(newEntity.EntityKey.EntitySetName,newEntity); entities.SaveChanges(); } } 此方法部分适用于将对象的更改保存到数据库的位置,但不保存对相关对象关系的任何更改. 我有以下代码调用上面的方法作为我的例子: List<Territories> territories = GetTerritories(); List<Region> regions = GetRegions(); Region region = regions.Where(n => n.RegionID == 2).FirstOrDefault(); Territories oldTerritory = territories.Where(n => n.TerritoryID == "01581").FirstOrDefault(); Territories newTerritory = ObjectCopier.Clone<Territories>(oldTerritory); newTerritory.TerritoryDescription = "Hello World"; newTerritory.Region = region; SaveEntity(oldTerritory,newTerritory); 对TerritoryDe??scription的更改已成功保存,但对Region的更改不是,在数据库中它仍然保留为RegionID = 1而不是RegionID = 2. 任何人都可以向我提供一些见解,说明为什么ApplyPropertyChanges不会传播对相关对象的更改? 另外,有谁知道如何解决这个问题? 解决方法
不是单独获取区域和区域,而是在同一查询中获取它们.类似的东西(我假设你想要更新实体,不想创建一个新实体);
static List<Region> GetTerritoriesWithRegions() { using (NorthwindEntities entities = new NorthwindEntities()) { entities.Territories.MergeOption = System.Data.Objects.MergeOption.NoTracking; return entities.Territories.Include("Region").ToList(); } } 然后将它们更新为以下内容; List<Territories> territoriesWithRegions = GetTerritoriesWithRegions(); Territories territory = territories.Where(n => n.TerritoryID == "01581").FirstOrDefault(); territory.TerritoryDescription = "Hello World"; Region region = territories.Where(p => p.Any(q => q.Region.RegionID == 2)).FirstOrDefault().Region; territory.Region = region; SaveEntity(territory); 并拯救他们; static void SaveEntity(EntityObject entity) { using (NorthwindEntities entities = new NorthwindEntities()) { entities.Attach(entity); entities.Context.ObjectStateManager.ChangeObjectState(entity,EntityState.Modified); entities.SaveChanges(); } } 我在记事本上编码了这个,所以可能会有错误;如果有的话请评论,所以我会相应更新. (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |