如何跟踪与WCF RIA服务实体的变化？ [英] How to track entity changes with WCF Ria Services?

问题描述

我需要登录到客户端上发生的一个数据库表中的实体所做的更改。然而，当我修改和检查ChangeTracker属性，它声称没有发生变化。

I need to log changes made to an entity that occur on the client to a database table. However, when I make changes and inspect the ChangeTracker property, it claims that no changes have occurred.

[服务]

    private static readonly ISomeDao someDao = DataAccess.SomeDao;
    [Query]
    public List<SomeEntity> GetSomeEntites(int someId)
    {
        var entities = someDao.GetSomeEntites(someId);
        entities.ForEach(e => e.StartTracking());
        return entities;
    }

    [Update]
    public void UpdateSomeEntity(SomeEntity entity)
    {
        // inspect entity.ChangeTracker.OriginalValues.... nothing
        entity.StopTracking();
        // inspect entity.ChangeTracker.OriginalValues.... nothing
        ...
        // Update log table 
    }

[客户]

    public EntitySet<SomeEntity> SomeEntities
    {
        get { return _someEntity; }
        set
        {
            if (_someEntity!= value)
            {
                _someEntity= value;
                OnPropertyChanged("SomeEntities");
            }
        }
    }

所以，如果，自我跟踪实体和WCF RIA Services不能生活在一起（这就是我怀疑），如何做一个轨道的变化？

So, if, self-tracking entities and WCF Ria Services can't live together (which is what I'm suspecting), how does one track changes?

推荐答案

不要用RIA服务工作，但单独与WCF（不知道它使太大的区别...）。首先你没有执行命令（服务器端），以StartTracking这是通过WCF与反序列化自动完成的实体。

Don't work with Ria services but solely with WCF (don't know if it makes much difference...). First of all you don't have to execute the command (server-side) to StartTracking the entities this is done automatically with deserializing by WCF.

[OnDeserialized]
public void OnDeserializedMethod(StreamingContext context)
{
  IsDeserializing = false;
  ChangeTracker.ChangeTrackingEnabled = true;
}

其次，我知道的是，一个自我的唯一小学和外键的属性改变时跟踪实体被记录。这是不是为保持生活在一个实体上下文（那么所有的修改记录）NORMAL实体的情况下。

Second what I know is that only primary- and foreign key properties of a SELF tracking entity are recorded when changed. this is not the case for NORMAL entities that keep living in an entity context (then all changes are recorded).

如果您需要在自我跟踪 - 细看实体您可能会看到这样的事情：

If you take a closer look at a Self-Tracking-Entity you might see something like this:

    [DataMember]
    public string Plaats
    {
        get { return _plaats; }
        set
        {
            if (_plaats != value)
            {
                _plaats = value;
                OnPropertyChanged("Plaats");
            }
        }
    }
    private string _plaats;

    [DataMember]
    public int LandID
    {
        get { return _landID; }
        set
        {
            if (_landID != value)
            {
                ChangeTracker.RecordOriginalValue("LandID", _landID);
                if (!IsDeserializing)
                {
                    if (Land != null && Land.ID != value)
                    {
                        Land = null;
                    }
                }
                _landID = value;
                OnPropertyChanged("LandID");
            }
        }
    }
    private int _landID;

你看有什么区别？简单物业国家地点和外键属性LandID之间？这是该行`ChangeTracker.RecordOriginalValue（LandID，_landID）;

Do you see the difference? between the simple property Plaats and the Foreign key property LandID? It's in the line `ChangeTracker.RecordOriginalValue("LandID", _landID);

有关简单的属性这些变化并不被记录（属性themseklves是场外改变，所以。这EF背景下知道如何ApplyChanges和更新数据库）

For simple properties these changes are not recorded (the properties themseklves are off-course changed, so that EF context knows how to ApplyChanges and update the database).

可能的想法可能是：

1. 要自定义T4模板来记录原始值​​的每个属性


2. 要从基类，你可以放下一些框架，通过响应记录原始值​​派生的所有实体的PropertyChanged事件


3. 当更新的entites，第一次获得来自数据库的原始值和跟踪更改

希望这有助于！

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