如何在N层架构中通过wcf检测ObservableCollection中已更改的poco实体？

Question

I have following layers in my applicaiton Date Layer (reference to Model) Business Layer(reference to Model ,Data) Model Service(WCF)-(reference to Model,Business Layer) UI (WPF/Silver Light) - Connected via WCF service

How do i detect the changed poco entities in an ObservableCollection in UI layer? for sending it back to server from client side for saving ? instead of sending all data back to sever side(via WCF)?

or

how to perform add/delete/update operation on entities in the collection in UI layer?

I am using VS2010/2012 C# EF 5 ADO.NET POCOEntityGenerator With WCF Support(for generating .tt templates from Model.edmx) SQL Server 2012

Even though searched a lot of places I didn't find a proper solution.. please help if any ideas...

Thanks...

The method i followed to create My application is given below link

http://www.toplinestrategies.com/dotneters/net/wcf-entity-framework-and-n-tier-solutions-part-2/?lang=en/comment-page-1/#comment-1954

Answer 1

Only proper solution is to do the change tracking manually. Each POCO object will have IsDirty property and each property of this object will have IsDirty = true in it's setter.

One way to make it less manual would be to create a framework, that will create wrapper classes, that will do this for you, but this requires large dose of reflection and code-generation. Also, it will still require all properties to be defined as virtual.

But generally, you want to refrain from making UI that would require this kind of tracking. When you want to change an entity, load only that entity in Edit window.

Answer 2

POCOs are well-suited for transmitting data between client and server. However, if you're looking for objects to actually work with on client and/or server side you may want to consider using self-tracking entities (STE) as these entities contain logic to track their actual changes and status.

Yet a better solution is to use the N-Tier Entity Framework which provides functionality to work with EF in n-tier applications. See http://ntieref.codeplex.com/ for more details.

Answer 3

If you are using EF, then your entities have a 'HasChanges' flag you can test against before submitting changes to your context. eg

if (this.CurrentEntity.HasChanges || CurrentEntity.EntityState == EntityState.New)
{
this.SubjectContext.SubmitChanges(Submit_Completed, saveDetails);
}