我使用 Northwind 数据库作为这篇文章的示例,我在使用 Entity Framework 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领土和地区:
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,并在分离状态下为我提供所需的对象集合。
我还有一个名为 SaveEntity 的静态方法,它同时接收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情况,但不会保存对相关对象关系的任何更改。
我有以下代码调用上述方法作为示例:
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 TerritoryDescription 的更改已成功保存,但对 Region 的更改未成功保存,在数据库中它仍然是 RegionID=1 而不是 RegionID=2。
谁能告诉我为什么 ApplyPropertyChanges 不传播对相关对象的更改?
还有,有谁知道我该如何解决这个问题?
最佳答案
与其分别获取区域和领土,不如在同一个查询中获取它们。类似的东西(我假设你想更新实体,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();
}
}
然后按如下方式更新它们;
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);
并保存它们;
static void SaveEntity(EntityObject entity)
{
using (NorthwindEntities entities = new NorthwindEntities())
{
entities.Attach(entity);
entities.Context.ObjectStateManager.ChangeObjectState(entity, EntityState.Modified);
entities.SaveChanges();
}
}
我已经在记事本上编码了,所以可能会有错误;如果有的话请评论,我会相应地更新。
关于c# - Entity Framework - 在分离状态下保存对相关对象的更改,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/1696641/