gtkmm menu bar not being displayed

Question

Hello am trying to write a program using gtkmm and ran into some problem, the was following the online tutorial on the gnome website. Although my program compiles and executes the menu bar is not being displayed, also shortcut key doesn’t work.

But I get a warning on the terminal Gtk-WARNING **: File: missing action File

Any pointers will helpful. Thank you

And this is the code for creating menu

mActionGroup = Gtk::ActionGroup::create();
mActionGroup->add(Gtk::Action::create("File", "_File"));
mActionGroup->add(
    Gtk::Action::create( "Open", Gtk::Stock::OPEN, "_Open", "Open a file" ),
    Gtk::AccelKey( "<control>o" ),
    sigc::mem_fun( *this, &myWindow::onFileOpen ) );

std::string menuInfo =
    std::string("<ui>")+
    "  <menubar name='MenuBar'>"+
    "    <menu action='File'>"+
    "      <menuitem action='Open'/>"+
    "    </menu>"+
    "  </menubar>"+
    "</ui>";
mUIManager = Gtk::UIManager::create();
add_accel_group(mUIManager->get_accel_group());
try
{
    mUIManager->add_ui_from_string( menuInfo );
}
catch( const Glib::Error &ex )
{
    ERROR( "Could not create menu" << ex.what() )
}
Gtk::Widget *pMenu = mUIManager->get_widget( "/MenuBar" );

mBox.pack_start( *pMenu, Gtk::PACK_SHRINK );
show_all_children();

this is the Gtkmm package installed libgtkmm-3.0-dev:amd64 and I compile using pkg-config --libs gtkmm-3.0 this gives these libraries

-lgtkmm-3.0 -latkmm-1.6 -lgdkmm-3.0 -lgiomm-2.4 -lpangomm-1.4 -lgtk-3 -lglibmm-2.4     
-lcairomm-1.0 -lgdk-3 -latk-1.0 -lgio-2.0 -lpangocairo-1.0 -lgdk_pixbuf-2.0 -lcairo-gobject 
-lpango-1.0 -lcairo -lsigc-2.0 -lgobject-2.0 -lglib-2.0  

EDIT:

not sure how to check my gtkmm version but i searched the package name and got this marked as superseded [https://launchpad.net/ubuntu/saucy/amd64/libgtkmm-3.0-dev/3.6.0-0ubuntu1] so i think the version is 3.6