wmi win32_devicechangeevent - wrong eventuality form returned?

i am perplexing register "device added/ device removed" eventuality controlling wmi. i contend device - i meant something lines disk-on-key any device files i access...

i am arising event, eventuality raised, nonetheless eventtype propery opposite i am awaiting see.

the support () states : 1- config change, 2- device added, 3-device private 4- docking. reason i always value 1.

any ideas ?

here's illustration formula :

public category wmireceiveevent
{
    open wmireceiveevent()
    {
        try
        {
            wqleventquery query = new wqleventquery(
                "select * win32_devicechangeevent");

            managementeventwatcher spectator = new managementeventwatcher(query);
            console.writeline("waiting an event...");

            watcher.eventarrived += 
                new eventarrivedeventhandler(
                handleevent);

            // start listening events
            watcher.start();

            // something while sharp events
            system.threading.thread.sleep(10000);

            // stop listening events
            watcher.stop();
            return;
        }
        catch(managementexception err)
        {
            messagebox.show("an blunder occurred while perplexing accept an event: " + err.message);
        }
    }

    private vacant handleevent(object sender,
        eventarrivedeventargs e)
    {
        console.writeline(e.newevent.getpropertyvalue["eventtype"]);
    }

    open stationary vacant main()
    {
        wmireceiveevent receiveevent = new wmireceiveevent();
        return;
    }
}