Databases
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    <p>In this situation I simply make the model expose <code>ObservableCollection</code>s rather than <code>List</code>s. There's no particular reason why it shouldn't. The <code>ObservableCollection</code> is in the <code>System.Collections.ObjectModel</code> namespace of the <code>System</code> assembly, so there's no unreasonable extra dependencies, you almost certainly have <code>System</code> anyway. <code>List</code> is in <code>mscorlib</code>, but that's as much a historical artefact as anything.</p> <p>This simplifies the model-viewmodel interactions massively, I can't see a reason not to do it, using <code>List</code>s on the model just creates lots of unpleasant boiler-plate code. You are interested in the events, after all.</p> <p>Also, why is your <code>HouseVM</code> wrapping an <code>ObservableCollection&lt;PeopleVM&gt;</code>, rather than <code>ObservableCollection&lt;People&gt;</code>? VMs are for binding to views, so I would think that whatever is binding to your <code>ObservableCollection&lt;PeopleVM&gt;</code> is actually interested in <code>People</code>, otherwise you're binding-within-a-binding, or is there a specific reason why this is useful? I wouldn't generally have a VM expose other VMs, but maybe that's just me.</p> <p><strong>Edit about libraries/WCF</strong></p> <p>I don't see why having a model in a library, or even exposed by a WCF-server should affect whether they raise events or not, it seems perfectly valid to me (obviously the WCF-service won't expose the events directly). If you don't like this, I think you're stuck with having to chain multiple updates, though I wonder if you're actually just manually doing the same work as the event would do in an <code>ObservableCollection</code>, unless I've misunderstood some of it.</p> <p>Personally, like I said, I'd keep the VMs simple, and have them expose the minimum and not expose other VMs. It can take some redesign and make certain parts a bit of a pain (e.g. <code>Converter</code>s, however, you end up with a simple, easy-to-manage design with some simple-to-handle irritations on the edges.</p> <p>It seems to me that your current route is going to end up very complex rather quickly and, most importantly, awkward to follow... However, YMMV, it's just my experience :)</p> <p>Perhaps moving some of the logic to explicit services might help?</p>
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    1. COGiving the Model an ObserbableCollection<Items> instead of List<Item>s still doesnt get me an ObserbableCollection<ItemsVM> - or have I misunderstood? And the Model shouldn't know about ItemVMs just about Items.
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    2. COPlus my models are in libraries and run in WCF servers etc - this is no place for ObservableCollections.
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    3. COThe question about VMs exposing VMs is valid. I do this because I have a view on my House - with bindings to HouseVM but I also have views on the House occupants - which require properties over the top of those exposed by just People - hence the need for PeopleVM.
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