Databinding ComboBox to GraphicsCollection - ESRI, WPF runtime

Question

I'd like to bind a GraphicsCollection (which is a property in a view model) to a combo box in a XAML window. The problem is I can't figure out how to display attribute values in the combo box. I can get it to display the Geometry property like this:

<ComboBox DataContext="{StaticResource MyViewModel}"
                DisplayMemberPath="Geometry"
                ItemsSource="{Binding CollectionOfGraphics}"  />

But I want to be able to do something like this that will display the OBJECTID or some other attribute:

<ComboBox DataContext="{StaticResource MyViewModel}"
                DisplayMemberPath="Attributes[&quot;OBJECTID&quot;]"
                ItemsSource="{Binding CollectionOfGraphics}"  />

I also tried this approach - unsuccessfully:

<ComboBox DataContext="{StaticResource MyViewModel}"
                DisplayMemberPath="Attributes[0]"
                ItemsSource="{Binding CollectionOfGraphics}"  />

Platform: ArcGIS 10.1, WPF Runtime 10.1.1

Solution based on Antti Kajanus's answer below:

<ComboBox DataContext="{StaticResource MyViewModel}"
                ItemsSource="{Binding CollectionOfGraphics}" >
     <ComboBox.ItemTemplate>
          <DataTemplate>
              <TextBlock Text="{Binding Attributes[OBJECTID]}"/>
          </DataTemplate>
     </ComboBox.ItemTemplate>
</ComboBox>

Note that the attributite name (OBJECTID) did not have to be quoted.

Answer 1

Instead of using DisplayMemberPath property try using ItemTemplate. You can access to Attributes collection with binding to {Binding Attributes[AttributeName]} in the ItemTemplate.

 <DataTemplate x:Key="MyDataTemplate">
     <TextBlock Text="{Binding Attributes[Title]}"/>
 </DataTemplate>

<ComboBox DataContext="{StaticResource MyViewModel}"
      ItemsSource="{Binding CollectionOfGraphics}"
      ItemTemplate="{StaticResource MyDataTemplate}"/>

I don't have now possibility to test if you can access to attribute from DisplayMemberPath but I remember that I had some issues with that on some point.