SelectedItem="{Binding TheProperty, PresentationTraceSources.TraceLevel=High}"

<system.diagnostics>
      <sources>
        <source name="TraceSourceApp"
          switchName="sourceSwitch"
          switchType="System.Diagnostics.SourceSwitch">
          <listeners>
            <add name="console"
              type="System.Diagnostics.ConsoleTraceListener">
              <filter type="System.Diagnostics.EventTypeFilter"
                initializeData="Warning"/>

private static TraceSource mySource =
            new TraceSource("TraceSourceApp");
static void Main(string[] args)
{
    mySource.TraceEvent(TraceEventType.Error, 1, "Error message.");
 
    // Change the event type for which tracing occurs.
    // The console trace listener must be specified 
    // in the configuration file. First, save the original
    // settings from the configuration file.