WPF TraceLevel problem

I'm applying TraceLevel to a DataGrid like this

        <DataGrid HorizontalAlignment="Stretch" Margin="12,12,12,12" VerticalAlignment="Stretch" ItemsSource="{Binding Vals, PresentationTraceSour开发者_高级运维ces.TraceLevel=High}" />

but it doesn't produce any trace output. What's wrong?

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Tools -> Options -> Debugging -> Output Window -> WPF Trace Settings -> Data Binding

Set to warning or whatnot, think the default is off