I have a Silverlight control that has my root ViewModel object as it's data source. The ViewModel exposes a list of Cards as well as a SelectedCard property which is bound to a drop-down list at the top of the view. I then have a form of sorts at the bottom that displays the properties of the SelectedCard. My XAML appears as (reduced for simplicity):
<StackPanel Orientation="Vertical">
<ComboBox DisplayMemberPath="Name"
ItemsSource="{Binding Path=Cards}"
SelectedItem="{Binding Path=SelectedCard, Mode=TwoWay}"
/>
<TextBlock Text="{Binding Path=SelectedCard.Name}"
/>
<ListBox DisplayMemberPath="Name"
ItemsSource="{Binding Path=SelectedCard.PendingTransactions}"
/>
</StackPanel>
I would expect the TextBlock and ListBox to update whenever I select a new item in the ComboBox, but this is not the case. I'm sure it has to do with the fact that the TextBlock and ListBox are actually bound to properties of the SelectedCard so it is listening for property change notifications for the properties on that object. But, I would have thought that data-binding would be smart enough to recognize that the parent object in the binding expression had changed and update the entire binding.
It bears noting that the PendingTransactions property (bound to the ListBox) is lazy-loaded. So, the first time I select an item in the ComboBox, I do make the async call and load the list and the UI updates to display the information corresponding to the selected item. However, when I reselect an item, the UI doesn't change!
For example, if my original list contains three cards, I select the first card by default. Data-binding does attempt to access the PendingTransactions property on that Card object and updates the ListBox correctly. If I select the second card in the list, the same thing happens and I get the list of PendingTransactions for that card displayed. But, if I select the first card again, nothing changes in my UI! Setting a breakpoint, I am able to confirm that the SelectedCard property is being updated correctly.
How can I make this work???
