wpf combobox not binding to collection when inside ContentTemplate - wpf

Question

I'm trying show a certain control based on a property (combobox or textbox). So I have this contentcontrol implemented:
<!--<ComboBox MaxWidth="200" Background="#333333" ItemsSource="{Binding ModelObjectWrapper.Values}" Grid.Row="1" Grid.Column="1"/>-->
<ContentControl Grid.Row="1" Grid.Column="1">
<ContentControl.Resources>
<Style TargetType="ContentControl">
<Style.Triggers>
<DataTrigger Binding="{Binding ModelObjectWrapper.ObjType}" Value="typeA">
<Setter Property="ContentTemplate">
<Setter.Value>
<DataTemplate>
<ComboBox HorizontalAlignment="Left" MaxWidth="200" Background="#333333" ItemsSource="{Binding ModelObjectWrapper.Values, UpdateSourceTrigger=PropertyChanged}"/>
</DataTemplate>
</Setter.Value>
</Setter>
</DataTrigger>
<DataTrigger Binding="{Binding ModelObjectWrapper.ObjType}" Value="typeB">
<Setter Property="ContentTemplate">
<Setter.Value>
<DataTemplate>
<TextBox />
</DataTemplate>
</Setter.Value>
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</ContentControl.Resources>
</ContentControl>
The problem is that the combobox is not showing any items when its part of a controltemplate, and I know the bound list does have them, so I'm assuming the combobox is not being bound to the ItemsSource correctly.
The first line (having only a combobox without the templates), commented out, works fine. Am I not doing the binding right? Could it be that because its part of a datatrigger, it's not getting the right DataContext? I must note that the DataTrigger itself works great (IE showing a combobox if *.ObjType == "typeA".
The VM is a wrapper class around an object:
public class ModelObjectWrapper : ViewModelBase
{
private theModelObject model_obj;
public ModelObjectWrapper(theModelObject obj)
{
model_obj = obj;
}
public ObservableCollection<string> Values
{
get { return model_obj.Values; }
set
{
if (value == model_obj.Values)
return;
model_obj.Values = value;
OnPropertyChanged();
}
}
}

Answer 1

The DataContext of the root element in a ContentControl is the Content of the same ContentControl. Try to use a RelativeSource to bind to a property of the ContentControl's DataContext:
<ComboBox HorizontalAlignment="Left" MaxWidth="200" Background="#333333"
ItemsSource="{Binding DataContext.ModelObjectWrapper.Values, RelativeSource={RelativeSource AncestorType=ContentControl}}"/>
By the way, there is no point setting the UpdateSourceTrigger of an ItemsSource binding to PropertyChanged because the ComboBox never sets the source property.