Binding a DynamicResource

I'm trying to use a MultiBinding as the ItemsSource for a ListBox, and I want to bind a couple of collections to the MultiBinding. The collections aren't populated until after the host control (a derivation of Page) has already been instantiated. Just after being constructed, I call a method that sets up some of the data for the Page, including these collections.

Right now, I have something like this:

public void Setup()
{
    var items = MyObject.GetWithID(backingData.ID); // executes a db query to populate collection  
    var relatedItems = OtherObject.GetWithID(backingData.ID);
}

and I want to do something like this in XAML:

<Page ...

  ...

    <ListBox>
        <ListBox.ItemsSource>
            <MultiBinding Converter="{StaticResource converter}">
                <Binding Source="{somehow get items}"/>
                <Binding Source="{somehow get relatedItems}"/>
            </MultiBinding>
        </ListBox.ItemsSource>
    </ListBox>
  ...
</Page>

I know I can't use DynamicResource in a Binding, so what can I do?

From stackoverflow

• Sounds to me like what you really want is a CompositeCollection and to setup a DataContext for your Page.

  <Page x:Class="MyPage" DataContext="{Binding RelativeSource={RelativeSource Self}}">
      <Page.Resources>
          <CollectionViewSource Source="{Binding Items}" x:Key="items" />
          <CollectionViewSource Source="{Binding RelatedItems}" x:Key="relatedItems" />
      </Page.Resources>
  
      <ListBox>
         <ListBox.ItemsSource>
           <CompositeCollection>
             <CollectionContainer
               Collection="{StaticResource items}" />
             <CollectionContainer
               Collection="{StaticResource relatedItems}" />
           </CompositeCollection>
         </ListBox.ItemsSource>
      </ListBox>
  </Page>
  

  The Code behind would look something like this:

  public class MyPage : Page
  {
      private void Setup()
      {
          Items = ...;
          RelatedItems = ...;
      }
  
      public static readonly DependencyProperty ItemsProperty =
          DependencyProperty.Register("Items", typeof(ReadOnlyCollection<data>), typeof(MyPage),new PropertyMetadata(false));
      public ReadOnlyCollection<data> Items
      {
          get { return (ReadOnlyCollection<data>)this.GetValue(ItemsProperty ); }
          set { this.SetValue(ItemsProperty , value); } 
      }
  
      public static readonly DependencyProperty RelatedItemsProperty =
          DependencyProperty.Register("RelatedItems", typeof(ReadOnlyCollection<data>), typeof(MyPage),new PropertyMetadata(false));
      public ReadOnlyCollection<data> RelatedItems
      {
          get { return (ReadOnlyCollection<data>)this.GetValue(RelatedItemsProperty ); }
          set { this.SetValue(RelatedItemsProperty , value); } 
      }
  }
  

  Edit: I remembered that CollectionContainer doesn't participate in the logical tree so you need to use a CollectionViewSource and a StaticResource.