Question

I have inherited some Silverlight\WCF code and now need to implement some new features. I fairly new to Silverlight\WCF so my question may be rather basic. So…

I have a listbox in Silverlight that binds to a resource that is a List<> returned from a WCF (rest) service (which is just reading values from a db table). I have implemented the ability to add new items to the db table through a WCF service and now want to make my listbox update once it has been added to the db.

It is possible that my initial code needs to change so I have listed the relevant lines below.

In xaml the resource is as such:

<CollectionViewSource x:Key="myWCFSvc">
  <CollectionViewSource.SortDescriptions>
    <scm:SortDescription Direction="Ascending" PropertyName="ID" />
  </CollectionViewSource.SortDescriptions>
</CollectionViewSource>

And the binding of the listbox is:

ItemsSource="{Binding Source={StaticResource myWCFSvc}}

And the .cs has in the callback

((CollectionViewSource)LayoutRoot.Resources["WCFSvc"]).Source = myList;

So now if a user adds a new entry through another Silverlight childwindow an new entry is created in the db and I want to update the listbox to include this entry. I’m unclear how to do this.

I know there are observablecollections and INotifyPropertyChanged but unsure if this is those are what I need, or how to use them in this context. I searched around a bit but the examples I found don’t seem fit my scenario.

Answer 1

Your original thoughts are correct, the type you are looking for is the ObservableCollection<T>.

If you replace your existing List with this then as changes are made to its membership by other code it will notify other interested parties such as the CollectionViewSource, which in turn will notify anyting that is binding to it.