Unable to hook into PropertyChanged event using MVVM-Light - mvvm-light

Question

Greetings, creating my first MVVM based WPF app and trying to figure out why I'm unable to hook into the PropertyChanged event of a dependency property.
Code in the parent view model:
void createClients()
{
var clients = from client in Repository.GetClients()
select new ClientViewModel(Repository, client);
foreach (var client in clients)
{
client.PropertyChanged += onClientPropertyChanged;
}
Clients = new ViewableCollection<ClientViewModel>(clients);
Clients.CollectionChanged += onClientsCollectionChanged;
}
// Never gets called
void onClientPropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName == "Name")
{
//...
}
}
ViewableCollection is a simple extension of ObservableCollection to encapsulate a View.
In the ClientViewModel the setters are being called but RaisePropertyChanged isn't working as I would expect, because onClientPropertyChanged isn't being invoked. Both view models inherit from ViewModelBase.
public string Name
{
get { return client.Name; }
set
{
if (value == client.Name) return;
client.Name = value;
RaisePropertyChanged("Name");
}
}
If I wire up PropertyChanged to a method inside the ClientViewModel then it is being fired, so I'm stumped as to why this isn't working in the parent view model. Where am I going wrong?

Answer 1

This SO question explains the problem; ObservableCollection protects the PropertyChanged event.
One solution is to use MVVM-Light Messenger:
void createClients()
{
var clients = from client in Repository.GetClients()
select new ClientViewModel(Repository, client);
Clients = new ViewableCollection<ClientViewModel>(clients);
Clients.CollectionChanged += onClientsCollectionChanged;
Messenger.Default.Register<PropertyChangedMessage<string>>(this, (pcm) =>
{
var clientVM = pcm.Sender as ClientViewModel;
if (clientVM != null && pcm.PropertyName == "Name")
{
// ...
}
});
}
createClients() should be refactored, but for consistency with the question code I'll leave it in there. Then a slight change to the property setter:
public string Name
{
get { return client.Name; }
set
{
if (value == client.Name) return;
string oldValue = client.Name;
client.Name = value;
RaisePropertyChanged<string>("Name", oldValue, value, true);
}
}