wcf-ria-services - WCF RIA Services / intercept or subscribe to a RaiseDataMemberChanging

Question

So I'm new to the concept of routed events, but I know that messages are flying everywhere when fields are changing via the RaiseDataMemberChanging / RaiseDataMemberChanged messages.

The quick question is how to I "listen" for those routed messages?

I would like my view model, in a MVVM correct matter, intercept a message that a field is being updated, deep down in the heirarchy of tables. If a change occurs in a child (a date range), that date range change has some business logic associated with it that works from top down.

I've know that I can use partial methods to inject code during the changing and changed events, but the design (one to one relationship) means that a change to the child, in the context of the child, has no reference the parent (Parent has a one to one reference to child, but child has no reference to parent).

Yes I can add the reference from the child to the parent (making the parent have both a one to one, as well as a one to many relationship), but during creation of the entity, this creates a problem - parent has to exist before the child entity exists, and the child entity has to exist before a reference to the parent can exist. This design requires an insert of the parent, and child, then an update of the child - which confuses WCF RIA Services during the inital creation process.

Sorry for the long winded explaination, but I'll even consider design changes if this all makes sense to anyone that cares to comment.

Any input would be appreciated.

Answer 1

我正在使用对相关实体的 PropertyChanged 事件的订阅。过滤掉几个字段的所有事件似乎需要做很多工作。

使用 RX，我希望使用的资源是最少的，当使用强引用处理事件时，弱引用避免了内存链接问题：

        Observable.FromEventPattern<PropertyChangedEventArgs>(this.FlowEntity, "PropertyChanged")
      .Where(pPropertyChanged => (
                                 pPropertyChanged.EventArgs.PropertyName.EndsWith("Date")) ||
                                 pPropertyChanged.EventArgs.PropertyName == "Capacity"
                                 )
      .Subscribe(pObserver => this.RaiseFlowEntityDateChanged(this, pObserver.EventArgs));

FlowEntity 是我从父级监视的子实体。然后我使用父实体而不是实际持有事件的实体引发自定义事件。

我无法从部分方法中引发此事件，因为子实体没有父实体的上下文。