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    <p>Personally, I use an ObservableCollection in my model and my viewmodel.</p> <pre><code>class Model { public ObservableCollection&lt;Foo&gt; Foos; } class ViewModel { public Model Model; public ObservableCollection&lt;FooView&gt; Foos; public ViewModel() { Model.Foos.CollectionChanged += OnModelFoosCollection_CollectionChanged; } void OnModelFoosCollection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e) { Foo re; switch (e.Action) { case NotifyCollectionChangedAction.Add: re = e.NewItems[0] as Foo; if (re != null) AddFoo(re); //For other logic that may need to be applied break; case NotifyCollectionChangedAction.Remove: re = e.OldItems[0] as Foo; if (re != null) RemoveFoo(re); break; case NotifyCollectionChangedAction.Reset: Foos.Clear(); /* I have an AddRange in an ObservableCollection-derived class You could do Model.Foo.ForEach(ree =&gt; AddFoo(ree)); */ var converter = from ree in Model.Foo select new FooView(ree); Reports.AddRange(converter); break; default: //exercise for the reader :) s_ILog.Error("OnModelFoosCollection_CollectionChangedDid not deal with " + e.Action.ToString()); break; } } void AddFoo(Foo f) { Foos.Add(new FooView(f)); } void RemoveFoo(Foo f) { var match = from f in Foos where f.Model == f //if you have a unique id, that might be a faster comparison select f; if(match.Any()) Foos.Remove(match.First()); } } </code></pre> <p>Now, when you remove something from the Model's Foo collection, it will automatically remove the corresponding FooView. This corresponds with how I think about this sort of thing. If I want to delete something, the Model is where is really needs to be deleted.</p> <p>It feels like a lot of code, but it isn't that much, really. I'm sure one could build a generic version of this, but IMO you always end up wanting custom logic dealing with addition/removal of elements.</p>
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    1. POBi-directional view model syncing with "live" collections and properties
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    1. COOK this makes sense and was the conclusion that I came to. I still want to see more evidence of other peoples approaches to give me confidence this is "the best way". For example I have never seen this approach in a sample or blog post :-/
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    2. COWhat if the model only exposes an IList or something? Turning every list in your program into an ObservableCollection is not a solution. What if your model doesn't implement INotifyPropertyChanged? Listening to an ObservableCollection in the ViewModel and then pushing the changes back to the model works fine, but you can't expect the model to offer you such amenities, and in many cases ObservableCollection might not provide the functionality you need in your model.
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      1. USBenny Jobigan
    3. COI tend to do more of the Sacha Barber style MVVM. I'm writing new code, I don't have legacy Models, so I rarely even have a model at all. In general, if I want INPC, I write it. If I need ObservableCollection, I use it.
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