completed the branch

src/Shared/HandyControl_Shared/Controls/SideMenu/SideMenu.cs

@@ -1,6 +1,7 @@
-using System.Windows;
+using System;
+using System.Linq;
+using System.Windows;
 using HandyControl.Data;
-using HandyControl.Data.Enum;
 
 namespace HandyControl.Controls
 {
@@ -15,6 +16,22 @@ namespace HandyControl.Controls
         public SideMenu()
         {
             AddHandler(SideMenuItem.SelectedEvent, new RoutedEventHandler(SideMenuItemSelected));
+
+            Loaded += (s, e) => Init();
+        }
+
+        protected override void Refresh()
+        {
+            base.Refresh();
+
+            Init();
+        }
+
+        private void Init()
+        {
+            if (ItemsHost == null) return;
+
+            OnExpandModeChanged(ExpandMode);
         }
 
         private void SideMenuItemSelected(object sender, RoutedEventArgs e)
@@ -23,6 +40,8 @@ namespace HandyControl.Controls
             {
                 if (item.Role == SideMenuItemRole.Item)
                 {
+                    if (Equals(item, _selectedItem)) return;
+
                     if (_selectedItem != null)
                     {
                         _selectedItem.IsSelected = false;
@@ -30,6 +49,10 @@ namespace HandyControl.Controls
 
                     _selectedItem = item;
                     _selectedItem.IsSelected = true;
+                    RaiseEvent(new FunctionEventArgs<object>(SelectionChangedEvent, this)
+                    {
+                        Info = e.OriginalSource
+                    });
                     _isItemSelected = true;
                 }
                 else
@@ -38,20 +61,36 @@ namespace HandyControl.Controls
                     {
                         if (_selectedHeader != null)
                         {
+                            if (ExpandMode == ExpandMode.Freedom && item.ItemsHost.IsVisible && !_isItemSelected)
+                            {
+                                item.IsSelected = false;
+                                SwitchPanelArea(item);
+                                return;
+                            }
+
                             _selectedHeader.IsSelected = false;
-                            SwitchPanelArea(_selectedHeader);
+                            if (ExpandMode != ExpandMode.Freedom)
+                            {
+                                SwitchPanelArea(_selectedHeader);
+                            }
                         }
 
                         _selectedHeader = item;
                         _selectedHeader.IsSelected = true;
                         SwitchPanelArea(_selectedHeader);
                     }
+                    else if (ExpandMode == ExpandMode.Freedom && !_isItemSelected)
+                    {
+                        _selectedHeader.IsSelected = false;
+                        SwitchPanelArea(_selectedHeader);
+                        _selectedHeader = null;
+                    }
 
                     if (_isItemSelected)
                     {
                         _isItemSelected = false;
                     }
-                    else
+                    else if(_selectedHeader != null)
                     {
                         _selectedHeader.SelectDefaultItem();
                         _isItemSelected = false;
@@ -67,6 +106,7 @@ namespace HandyControl.Controls
                 case ExpandMode.ShowAll:
                     return;
                 case ExpandMode.ShowOne:
+                case ExpandMode.Freedom:
                 case ExpandMode.Accordion:
                     oldItem.SwitchPanelArea(oldItem.IsSelected);
                     break;
@@ -78,12 +118,72 @@ namespace HandyControl.Controls
         protected override bool IsItemItsOwnContainerOverride(object item) => item is SideMenuItem;
 
         public static readonly DependencyProperty ExpandModeProperty = DependencyProperty.Register(
-            "ExpandMode", typeof(ExpandMode), typeof(SideMenu), new PropertyMetadata(default(ExpandMode)));
+            "ExpandMode", typeof(ExpandMode), typeof(SideMenu), new PropertyMetadata(default(ExpandMode), OnExpandModeChanged));
+
+        private static void OnExpandModeChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+        {
+            var ctl = (SideMenu) d;
+            var v = (ExpandMode) e.NewValue;
+
+            if (ctl.ItemsHost == null)
+            {
+                return;
+            }
+
+            ctl.OnExpandModeChanged(v);
+        }
+
+        private void OnExpandModeChanged(ExpandMode mode)
+        {
+            if (mode == ExpandMode.ShowAll)
+            {
+                ShowAll();
+            }
+            else if (mode == ExpandMode.ShowOne)
+            {
+                var sideMenuItem = ItemsHost.Children.OfType<SideMenuItem>().FirstOrDefault(item => item.IsSelected);
+                ShowSelectedOne(sideMenuItem);
+            }
+        }
 
         public ExpandMode ExpandMode
         {
             get => (ExpandMode) GetValue(ExpandModeProperty);
             set => SetValue(ExpandModeProperty, value);
         }
+
+        public static readonly DependencyProperty PanelAreaLengthProperty = DependencyProperty.Register(
+            "PanelAreaLength", typeof(double), typeof(SideMenu), new PropertyMetadata(double.NaN));
+
+        public double PanelAreaLength
+        {
+            get => (double) GetValue(PanelAreaLengthProperty);
+            set => SetValue(PanelAreaLengthProperty, value);
+        }
+
+        private void ShowAll()
+        {
+            foreach (var sideMenuItem in ItemsHost.Children.OfType<SideMenuItem>())
+            {
+                sideMenuItem.SwitchPanelArea(true);
+            }
+        }
+
+        private void ShowSelectedOne(SideMenuItem item)
+        {
+            foreach (var sideMenuItem in ItemsHost.Children.OfType<SideMenuItem>())
+            {
+                sideMenuItem.SwitchPanelArea(Equals(sideMenuItem, item));
+            }
+        }
+
+        public static readonly RoutedEvent SelectionChangedEvent = EventManager.RegisterRoutedEvent(
+            "SelectionChanged", RoutingStrategy.Bubble, typeof(EventHandler<FunctionEventArgs<object>>), typeof(SideMenu));
+
+        public event EventHandler<FunctionEventArgs<object>> SelectionChanged
+        {
+            add => AddHandler(SelectionChangedEvent, value);
+            remove => RemoveHandler(SelectionChangedEvent, value);
+        }
     }
 }

src/Shared/HandyControl_Shared/Controls/SideMenu/SideMenuItem.cs

@@ -1,5 +1,6 @@
 using System.Linq;
 using System.Windows;
+using System.Windows.Data;
 using System.Windows.Input;
 using HandyControl.Data;
 using HandyControl.Tools.Extension;
@@ -19,6 +20,54 @@ namespace HandyControl.Controls
             set => SetValue(IconProperty, value);
         }
 
+        public SideMenuItem()
+        {
+            SetBinding(ExpandModeProperty, new Binding(SideMenu.ExpandModeProperty.Name)
+            {
+                RelativeSource = new RelativeSource(RelativeSourceMode.FindAncestor, typeof(SideMenu), 1)
+            });
+        }
+
+        internal static readonly DependencyProperty ExpandModeProperty =
+            SideMenu.ExpandModeProperty.AddOwner(typeof(SideMenuItem), new PropertyMetadata(default(ExpandMode)));
+
+        internal ExpandMode ExpandMode
+        {
+            get => (ExpandMode) GetValue(ExpandModeProperty);
+            set => SetValue(ExpandModeProperty, value);
+        }
+
+        protected override void Refresh()
+        {
+            if (ItemsHost == null) return;
+
+            ItemsHost.Children.Clear();
+            foreach (var item in Items)
+            {
+                DependencyObject container;
+                if (IsItemItsOwnContainerOverride(item))
+                {
+                    container = item as DependencyObject;
+                }
+                else
+                {
+                    container = GetContainerForItemOverride();
+                    PrepareContainerForItemOverride(container, item);
+                }
+
+                if (container is FrameworkElement element)
+                {
+                    element.Style = ItemContainerStyle;
+                    ItemsHost.Children.Add(element);
+                }
+            }
+
+            if (IsLoaded)
+            {
+                SwitchPanelArea(ExpandMode == ExpandMode.ShowAll || IsSelected);
+            }
+        }
+
         protected virtual void OnSelected(RoutedEventArgs e) => RaiseEvent(e);
 
         public static readonly RoutedEvent SelectedEvent =
@@ -91,11 +140,12 @@ namespace HandyControl.Controls
             }
         }
 
-        internal void SwitchPanelArea(bool close)
+        internal void SwitchPanelArea(bool isShow)
         {
+            if (ItemsHost == null) return;
             if (Role == SideMenuItemRole.Header)
             {
-                ItemsHost.Show(close);
+                ItemsHost.Show(isShow);
             }
         }
     }