MultiTerm/MultiTerm.Wpf/Controls/MenuItemExtensions.cs

using System;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;

namespace MultiTerm.Wpf.Controls
{
    /// <summary>
    /// TODO ueberarbeiten
    /// FROM:
    /// https://stackoverflow.com/questions/3652688/mutually-exclusive-checkable-menu-items/11497189#11497189
    /// </summary>
    public class MenuItemExtensions : MenuItem
    {
        private static MenuItem? previouslySelectedMenuItem = null;
        public static Dictionary<MenuItem, String> ElementToGroupNames = new Dictionary<MenuItem, String>();

        public static readonly DependencyProperty GroupNameProperty =
            DependencyProperty.RegisterAttached("GroupName",
                typeof(String),
                typeof(MenuItemExtensions),
                new PropertyMetadata(String.Empty, OnGroupNameChanged));

        public static readonly RoutedEvent IsCheckedChangedEvent =
            EventManager.RegisterRoutedEvent("IsCheckedChanged",
                RoutingStrategy.Bubble, typeof(RoutedEventArgs),
                typeof(MenuItemExtensions));

        public event RoutedEventHandler IsCheckedChanged
        {
            add { this.AddHandler(IsCheckedChangedEvent, value); }
            remove { this.RemoveHandler(IsCheckedChangedEvent, value); }
        }

        public static void SetGroupName(MenuItem element, String value)
        {
            element.SetValue(GroupNameProperty, value);
        }

        public static String GetGroupName(MenuItem element)
        {
            return element.GetValue(GroupNameProperty).ToString();
        }

        private static void OnGroupNameChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            //Add an entry to the group name collection
            var menuItem = d as MenuItem;
            var parent = menuItem.Parent as MenuItem;

            if (menuItem != null)
            {
                String newGroupName = e.NewValue.ToString();
                String oldGroupName = e.OldValue.ToString();
                if (String.IsNullOrEmpty(newGroupName))
                {
                    //Removing the toggle button from grouping
                    RemoveCheckboxFromGrouping(menuItem);
                }
                else
                {
                    //Switching to a new group
                    if (newGroupName != oldGroupName)
                    {
                        if (!String.IsNullOrEmpty(oldGroupName))
                        {
                            //Remove the old group mapping
                            RemoveCheckboxFromGrouping(menuItem);
                        }
                        ElementToGroupNames.Add(menuItem, e.NewValue.ToString());
                        menuItem.IsCheckable = true;
                        menuItem.Checked += MenuItemChecked;
                    }
                }
            }
        }

        private static void RemoveCheckboxFromGrouping(MenuItem checkBox)
        {
            ElementToGroupNames.Remove(checkBox);
            checkBox.Checked -= MenuItemChecked;
        }


        static void MenuItemChecked(object sender, RoutedEventArgs e)
        {
            var menuItem = e.OriginalSource as MenuItem;
            foreach (var item in ElementToGroupNames)
            {
                // uncheck all other menu items in group
                if (item.Key != menuItem && item.Value == GetGroupName(menuItem))
                {
                    item.Key.IsChecked = false;
                }
            }
            // raise routed event
            var menuItemExtensions = menuItem as MenuItemExtensions;
            if(previouslySelectedMenuItem != null && previouslySelectedMenuItem != menuItem)
            {
                RoutedEventArgs args = new RoutedEventArgs(IsCheckedChangedEvent);
                menuItemExtensions.RaiseEvent(args);
            }
            previouslySelectedMenuItem = menuItem;
        }
    }
}