我有一个我继承的基类,它与其他实体有两个零到多的关系:
public abstract class WebObject
{
public WebObject()
{
RelatedTags = new List<Tag>();
RelatedWebObjects = new List<WebObject>();
}
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid Id { get; set; }
public string MetaKeywords { get; set; }
public string MetaDescription { get; set; }
[InverseProperty("WebObjects")]
public virtual WebSite WebSite { get; set; }
[Required(ErrorMessage = "Every WebObject must be associated with a WebSite.")]
public Guid WebSiteId { get; set; }
public virtual ICollection<Tag> RelatedTags { get; set; }
public IList<Guid> RelatedTagIds { get; set; }
public virtual ICollection<WebObject> RelatedWebObjects { get; set; }
public IList<Guid> RelatedWebObjectIds { get; set; }
}
在SaveChanges期间使用ChangeTracker查看实体时,我很难获得这些关系的原始值(RelatedWebObjects&amp; RelatedTags)。我可以看到之前和之后的所有标量值,我可以看到新的关系,但我看不到旧的关系。我尝试过使用Member和Collection方法,但那些只显示当前值;不是旧的。另外我不喜欢使用它们,因为它需要我知道导航属性的名称,这不够通用。
我可以找到关系正在改变的相关对象,但当然这些相关对象中的值没有改变,所以这也没有任何帮助。
使用ChangeTracker在SaveChanges期间跟踪实体之前的关系是否有一些干净的方式?
以下是我正在处理的代码部分:
public override int SaveChanges()
{
List<AuditObject> auditTrailList = new List<AuditObject>();
foreach (DbEntityEntry entity in ChangeTracker.Entries().Where(obj => { return obj.State == EntityState.Added || obj.State == EntityState.Modified || obj.State == EntityState.Deleted; }))
{
if (!(entity.Entity is AuditObject))
{
AuditObject auditObject = new AuditObject();
auditObject.Id = Guid.NewGuid();
auditObject.RevisionStamp = DateTime.Now;
auditObject.UserName = HttpContext.Current.User.Identity.Name;
auditObject.EntityType = Utilities.GetCleanClassNameIfProxyClass(entity.Entity.GetType().Name);
if (entity.State == EntityState.Added)
auditObject.Action = EntityState.Added.ToString();
else if (entity.State == EntityState.Modified)
auditObject.Action = EntityState.Modified.ToString();
else if (entity.State == EntityState.Deleted)
auditObject.Action = EntityState.Deleted.ToString();
DbMemberEntry t1 = entity.Member("RelatedWebObjects");
// cannot find original relationship collection...
DbCollectionEntry t2 = entity.Collection("RelatedWebObjects");
// cannot find original relationship collection...
if (entity.State == EntityState.Added || entity.State == EntityState.Modified)
{
XDocument currentValues = new XDocument(new XElement(auditObject.EntityType));
foreach (string propertyName in entity.CurrentValues.PropertyNames)
{
currentValues.Root.Add(new XElement(propertyName, entity.CurrentValues[propertyName]));
}
auditObject.NewData = Regex.Replace(currentValues.ToString(), @"\r\n+", " ");
}
if (entity.State == EntityState.Modified || entity.State == EntityState.Deleted)
{
XDocument originalValues = new XDocument(new XElement(auditObject.EntityType));
foreach (string propertyName in entity.OriginalValues.PropertyNames)
{
originalValues.Root.Add(new XElement(propertyName, entity.OriginalValues[propertyName]));
}
auditObject.OldData = Regex.Replace(originalValues.ToString(), @"\r\n+", " ");
}
auditTrailList.Add(auditObject);
}
}
foreach (var audit in auditTrailList)
this.AuditObjects.Add(audit);
return base.SaveChanges();
}
答案 0 :(得分:13)
这有点困难。首先,您必须区别于EF提供的two types of relationships:
现在,如果您想知道外键关联的先前值,您只需要跟踪已公开外键属性的从属实体中的更改 - 这与跟踪任何其他属性更改完全相同。
如果您想跟踪独立关联中的更改,则情况会变得更难,因为DbContext API doesn't provide operations to track them。您必须恢复为ObjectContext
API及其ObjectStateManager
。
ObjectContext objectContext = ((IObjectContextAdapter)dbContext).ObjectContext;
foreach (ObjectStateEntry entry = objectContext.ObjectStateManager
.GetObjectStateEntries(~EntityState.Detached)
.Where(e => e.IsRelationship))
{
// Track changes here
}
现在您可以访问关系的ObjectStateEntry
个实例。这些实例永远不应该具有状态Modified
。它们将是Added
,Deleted
或Unchanged
,因为“修改”会被处理为删除旧关系并添加新关系。 ObjectStateEntry
还包含CurrentValues
和OriginalValues
个集合。这些集合还应包含两个项目,每个项目代表关系一侧的EntityKey
实体。
答案 1 :(得分:4)
由于EF更改会跟踪图表中的每个对象,因此您始终可以将图表中的任何实例传递给更改跟踪器,它会为您提供更改跟踪值。例如,以下代码将获取AuditObject的导航属性的原始/当前值:
DbMemberEntry t1 = entity.Member("RelatedWebObjects");
// cannot find original relationship collection....
AuditObject currentAuditObject = (AuditObject) entity;
var currValues = this.Entry(currentAuditObject.RelatedWebObjects).CurrentValues;
var orgValues = this.Entry(currentAuditObject.RelatedWebObjects).OriginalValues;
或者,在处理集合类型导航属性时,您可以应用相同的技巧:
DbCollectionEntry t2 = entity.Collection("RelatedWebObjects");
// cannot find original relationship collection....
foreach (WebObject item in currentAuditObject.RelatedWebObjects)
{
var currValues = this.Entry(item).CurrentValues;
}