Trying to change Background color of TextBox within RadComboBox

[Mark]

I am trying to color the Background of the TextBox within the RadComoboBox to be Pink is the search typed in fails.

<Style TargetType="TextBox" x:Key="CustomComboTextBoxStyle"  >
    <Style.Triggers>
        <DataTrigger Binding="{Binding SearchFailed}" Value="true">
            <Setter Property="Background" Value="LightPink" />
        </DataTrigger>
        <DataTrigger Binding="{Binding SearchFailed}" Value="false">
            <Setter Property="Background" Value="White" />
        </DataTrigger>
    </Style.Triggers>
</Style>

 

When I run, the SearchFailed is false and the background is white and that appears to work.  But when SearchFailed is true, the background does not change.

public bool SearchFailed
{
    get { return _searchFailed; }
    set
    {
        _searchFailed = value;
        NotifyPropertyChanged( "SearchFailed" );
    }
}

Is there something I need to do to tell the RadComboBox to update?

[Mark]

I solved but adding NotifyOnSourceUpdated=True on BOTH not just one.