MenuItemActionBarAction will call teh main activitiess "OnOptionsItemSelected", which allows us to re-use code.
Inheritance: ActionBarAction
        private void SetupMainActionBar()
        {
            if (DarkMenuId == Resource.Menu.MainMenu)
                return;

            ActionBar.TitleRaw = Resource.String.title_tasks;

            ActionBar.RemoveAllActions();

            var
            action = new MenuItemActionBarAction(this, this, Resource.Id.menu_sort, Resource.Drawable.ic_menu_sort,
                                                   Resource.String.menu_string_sort) { ActionType = ActionType.Never };

            ActionBar.AddAction(action);

            action = new MenuItemActionBarAction(this, this, Resource.Id.menu_delete_all, Resource.Drawable.ic_menu_delete_all,
                                                     Resource.String.menu_string_delete_all)
                             {ActionType = ActionType.Never};

            ActionBar.AddAction(action);

            action = new MenuItemActionBarAction(this, this, Resource.Id.menu_history, Resource.Drawable.ic_menu_history,
                                                     Resource.String.menu_string_history) { ActionType = ActionType.Never };

            ActionBar.AddAction(action);

            action = new MenuItemActionBarAction(this, this, Resource.Id.menu_about, Resource.Drawable.ic_menu_settings,
                                                     Resource.String.menu_string_about) {ActionType = ActionType.Never};
            ActionBar.AddAction(action);

            DarkMenuId = Resource.Menu.MainMenu;
            MenuId = Resource.Menu.MainMenu;

            m_AddButton.Visibility = ViewStates.Visible;
            ListView.Enabled = true;
            m_Editing = false;
        }
        private void SetupMainActionBar()
        {
            ActionBar.RemoveAllActions();

            var action = new MenuItemActionBarAction(this, this, Resource.Id.menu_share, Settings.UseLightIcons ? Resource.Drawable.ic_action_share : Resource.Drawable.ic_action_share_dark,
                                                   Resource.String.menu_string_share_history) { ActionType = ActionType.Always };

            ActionBar.AddAction(action);

            ActionBar.Title = ActionBar.Title + " - " + m_AllTasks.Count;

            DarkMenuId = Resource.Menu.HistoryMenu;
            MenuId = Resource.Menu.HistoryMenu;
        }
        private void SetupEditActionBar()
        {
            if (DarkMenuId == Resource.Menu.MainMenuEdit)
                return;

            ActionBar.TitleRaw = Resource.String.title_edit_task;
            ActionBar.RemoveAllActions();

            var action = new MenuItemActionBarAction(this, this, Resource.Id.menu_cancel_save, Settings.UseLightIcons ? Resource.Drawable.ic_action_cancel : Resource.Drawable.ic_action_cancel_dark,
                                                     Resource.String.menu_string_cancel) { ActionType = ActionType.Always };
            ActionBar.AddAction(action);

            action = new MenuItemActionBarAction(this, this, Resource.Id.menu_save, Settings.UseLightIcons ? Resource.Drawable.ic_action_save : Resource.Drawable.ic_action_save_dark,
                                                   Resource.String.menu_string_save) { ActionType = ActionType.Always };
            ActionBar.AddAction(action);

            DarkMenuId = Resource.Menu.MainMenuEdit;
            MenuId = Resource.Menu.MainMenuEdit;

            m_AddButton.Visibility = ViewStates.Gone;
            ListView.Enabled = false;
            m_Editing = true;
        }