_debugEvents.OnEnterBreakMode is not firing

publicclass MyDebugger
    {privatereadonly DTE _dte;privatereadonly EnvDTE.DebuggerEvents _debugEvents;publicevent _dispDebuggerEvents_OnEnterBreakModeEventHandler OnEnterBreakMode;public MyDebugger()
        {
            _dte = (DTE)Package.GetGlobalService(typeof(DTE));
            _debugEvents = _dte.Events.DebuggerEvents;
            _debugEvents.OnEnterBreakMode += new _dispDebuggerEvents_OnEnterBreakModeEventHandler(_debugEvents_OnEnterBreakMode);
            _debugEvents.OnEnterRunMode += new _dispDebuggerEvents_OnEnterRunModeEventHandler(_debugEvents_OnEnterRunMode);
            _debugEvents.OnContextChanged += new _dispDebuggerEvents_OnContextChangedEventHandler(_debugEvents_OnContextChanged);
            _debugEvents.OnEnterDesignMode += new _dispDebuggerEvents_OnEnterDesignModeEventHandler(_debugEvents_OnEnterDesignMode);
        }
}