c# - WPF TraceLevel problem -

i'm applying tracelevel datagrid this

        <datagrid horizontalalignment="stretch" margin="12,12,12,12" verticalalignment="stretch" itemssource="{binding vals, presentationtracesources.tracelevel=high}" /> 

but doesn't produce trace output. what's wrong?

tools -> options -> debugging -> output window -> wpf trace settings -> data binding

set warning or whatnot, think default off