public AutoEnterExitTrace(IDiagnostics wd, TraceSource ts, string class_method)
 {
     _wd = wd;
     _ts = ts;
     _class_method = class_method;
     if (null != wd)
     {
         wd.WriteDiagnosticInfo(ts, TraceEventType.Verbose, TraceEventID.traceFunctionEntry, string.Format("tid:{0} Entering {1}", Thread.CurrentThread.ManagedThreadId, class_method));
     }
 }