在SaveChanges上使用ObjectContext进行实体框架审核

为了进行审计日志记录，我需要获取所有列的值，包括为数据库中的某个表修改的FK实体和关系实体。数据库基本上是为用户可以上传资源（文件、在线文档、图片等）的网站而建的，我有一个名为Material的表，它有多个多个二元和一个二元的关系，如Material - Audience、Material - Category、"材料上传器"、"材料权限Material -Tags等。我想记录Material发生的所有更改。例如，如果有人从材料中删除标签，那么我需要记录：

• [User12-12/12]-Happy标签已从Crappy材料中删除

到目前为止，我得到的是：我可以使用获得所有修改、添加、删除的ObjectStateEntries

context.ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Deleted | EntityState.Modified)

现在，我可以使用检查这个ObjectStateEntry是否是RelationShip

if (e.IsRelationship) {
    HandleRelationshipEntry(e);
}
else {
    HandleEntry(e);
}

在HandleEntry方法中（条目不是关系条目），我可以检查Entry的类型，在我的情况下是Material，所以我正在做：

// We care about only Material which are modifed
if (e.State != EntityState.Modified || !(e.Entity is Material))
    return;

一旦我知道Entry的类型是Material Entry，我就可以使用获取Material表中所有更改的列

e.CurrentValues[ARCHIVE_COLUMN].ToString() != e.OriginalValues[ARCHIVE_COLUMN].ToString()

此时，我可以记录Material表的所有非FK更改。但如果列是FK到其他entity，我就无法将该FK值解析为相应的Entity。我只知道CategoryID已经从42更改为76，但我无法解析Category本身的名称。我尝试了将DBDataRecord和CurrentValueRecord转换为EntityKey的方法，但它只是NULL。是否有任何方法可以使用ObjectStateManager来解决这些FKs到Entities？

我的完整代码供参考：

专用类SingleMaterialLogger{MaterialAuditData auditData=新材料auditData（）；public void HandleEntity（ObjectStateEntry e，ObjectContext上下文）{HandlePrimaryTypeChanges（e）；HandleComplexTypeChanges（e，context）；}

        private void HandleComplexTypeChanges(ObjectStateEntry e, ObjectContext c) {
            // Owner, Category, Contact
            ChangeValueHelper(e, CONTACT_COLUMN, (k1, k2) => {
                // get old value
                User old = c.GetObjectByKey(k1) as User;
                User current = c.GetObjectByKey(k2) as User;
            });
        }
        public void HandlePrimaryTypeChanges(ObjectStateEntry e) {
            // Name, Description, ArchiveDate, Status
            // Again no reflection is used - So change them if column name changes
            ChangeValueHelper<string>(e, NAME_COLUMN, (change) => auditData.Name = change);
            ChangeValueHelper<string>(e, NAME_COLUMN, (change) => auditData.Description = change);
            // TODO - Fix change value helper
            if (e.CurrentValues[ARCHIVE_COLUMN].ToString() != e.OriginalValues[ARCHIVE_COLUMN].ToString()) {
                auditData.ArchiveDate = new Change<DateTime?>(e.OriginalValues[ARCHIVE_COLUMN] as DateTime?, e.CurrentValues[ARCHIVE_COLUMN] as DateTime?);
            }
        }
        private void ChangeValueHelper(ObjectStateEntry e, string columnName, Action<EntityKey, EntityKey> func) {
            if (e.CurrentValues[columnName].ToString() != e.OriginalValues[columnName].ToString()) {
                func(e.OriginalValues[columnName] as EntityKey, e.CurrentValues[columnName] as EntityKey);
            }
        }
        private void ChangeValueHelper<T>(ObjectStateEntry e, string columnName, Action<Change<T>> func) where T : class {
            if(e.CurrentValues[columnName].ToString() != e.OriginalValues[columnName].ToString()) {
                func(new Change<T>(e.OriginalValues[columnName] as T, e.OriginalValues[columnName] as T));
            }
        }
    }

    Dictionary<EntityKey, SingleMaterialLogger> singleMaterialLoggerMap = new Dictionary<EntityKey, SingleMaterialLogger>();
    private ObjectContext context;
    public MaterialAuditLogger(ObjectContext context) {
        this.context = context;
    }
    public void AuditMaterialChanges() {
        // Grab everything thats being added/deleted/modified
        foreach(var e in context.ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Deleted | EntityState.Modified)) {
            if (e.IsRelationship) {
                HandleRelationshipEntity(e);
            }
            else {
                HandleEntity(e);
            }
        }
    }
    private void HandleEntity(ObjectStateEntry e) {
        // We care about only Material which are modifed
        if (e.State != EntityState.Modified || !(e.Entity is Material))
            return;
        var logger = SingleLogger(e.EntityKey);
        logger.HandleEntity(e, context);
    }
    private void HandleRelationshipEntity(ObjectStateEntry e) {
        // relations whose entity keys contains
    }
    private SingleMaterialLogger SingleLogger(EntityKey key) {
        if(singleMaterialLoggerMap.ContainsKey(key))
            return singleMaterialLoggerMap[key];
        SingleMaterialLogger logger = new SingleMaterialLogger();
        singleMaterialLoggerMap[key] = logger;
        return logger;
    }

DbContext.Set(entityType).Find(id)