HamburgerMenuItem Command improvements (#2921)

* Add feature for #2865
  - Implement the interface ICommandSource
  - Handle Command binding change to hook or unhook command executable
  - Listen to the new command stuff to enable or disable the HamburgerMenuItem
  - New `MahApps.Metro.Styles.HamburgerMenu` key for the HamburgerMenu style

* Update 1.5.0.md

Author: punker76

docs/release-notes/1.5.0.md

@@ -16,6 +16,8 @@
     + Add `HamburgerVisibility` property [UWPCommunityToolkit #1020](https://github.com/Microsoft/UWPCommunityToolkit/pull/1020)
     + Set `Content` for `HamburgerMenu` only if one of the inner ListBox controls has a selected item.
     + New `HamburgerMenuHeaderTemplate` property to set a header right of the HamburgerMenu button. [@SilverDragon135](https://github.com/SilverDragon135) [#2917](https://github.com/MahApps/MahApps.Metro/pull/2917)
+    + Implement the interface `ICommandSource` and handle Command binding change to hook or unhook command executable.
+    + Add `MahApps.Metro.Styles.HamburgerMenu` style key to the HamburgerMenu.
 - If `ShowInTaskbar = false`, when double click on the title bar of a minimized window, the window will be restored instead of maximized. [#2854](https://github.com/MahApps/MahApps.Metro/pull/2854) [@hausenism](https://github.com/hausenism)
 - Fix WindowCommands tab stop bug [#2858](https://github.com/MahApps/MahApps.Metro/pull/2858) [@neilt6](https://github.com/neilt6)
 - Don't overwrite cancellation for window close event [#2868](https://github.com/MahApps/MahApps.Metro/pull/2868) [@batzen](https://github.com/batzen)
@@ -92,3 +94,4 @@
 - [#2332](https://github.com/MahApps/MahApps.Metro/issues/2332) Calendar ignores IsTodayHighlighted property
 - [#2434](https://github.com/MahApps/MahApps.Metro/issues/2434) DataGridNumericUpDownColumn foreground color
 - [#2627](https://github.com/MahApps/MahApps.Metro/issues/2627) Inconsistent FloatingWatermark Alignment
+- [#2865](https://github.com/MahApps/MahApps.Metro/issues/2865) [Feature request]Enable/Disable of Hamburger Menu Item

src/MahApps.Metro.Samples/MahApps.Metro.Demo/MahApps.Metro.Demo.Shared/ExampleViews/HamburgerMenuSample.xaml

@@ -5,9 +5,12 @@
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
              xmlns:iconPacks="http://metro.mahapps.com/winfx/xaml/iconpacks"
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             xmlns:metroDemo="clr-namespace:MetroDemo"
+             xmlns:exampleViews="clr-namespace:MetroDemo.ExampleViews"
              d:DesignHeight="300"
              d:DesignWidth="400"
-             mc:Ignorable="d">
+             mc:Ignorable="d"
+             d:DataContext="{d:DesignInstance metroDemo:MainWindowViewModel}">
 
     <UserControl.Resources>
         <DataTemplate x:Key="HamburgerMenuItem" DataType="{x:Type controls:HamburgerMenuItem}">
@@ -47,14 +50,21 @@
     </UserControl.Resources>
 
     <Grid>
+        <Grid.RowDefinitions>
+            <RowDefinition Height="Auto" />
+            <RowDefinition Height="*" />
+        </Grid.RowDefinitions>
+        <StackPanel Orientation="Horizontal" Grid.Row="0" Margin="20 5">
+            <CheckBox VerticalAlignment="Center" Content="Allow About Hamburger MenuItem" IsChecked="{Binding CanShowHamburgerAboutCommand, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
+        </StackPanel>
         <controls:HamburgerMenu x:Name="HamburgerMenuControl"
+                                Grid.Row="1"
                                 VerticalScrollBarOnLeftSide="False"
                                 SelectedIndex="1"
-                                Margin="20"
+                                Margin="20 0 20 20"
                                 HamburgerWidth="48"
                                 ItemClick="HamburgerMenu_OnItemClick"
                                 ItemTemplate="{StaticResource HamburgerMenuImageItem}"
-                                OptionsItemClick="HamburgerMenu_OnOptionsItemClick"
                                 OptionsItemTemplate="{StaticResource HamburgerMenuItem}">
             <!-- Header -->
             <controls:HamburgerMenu.HamburgerMenuHeaderTemplate>
@@ -80,7 +90,8 @@
             <!--  Options  -->
             <controls:HamburgerMenu.OptionsItemsSource>
                 <controls:HamburgerMenuItemCollection>
-                    <controls:HamburgerMenuGlyphItem Label="About">
+                    <controls:HamburgerMenuGlyphItem Label="About"
+                                                     Command="{x:Static exampleViews:ShowAboutCommand.Command}">
                         <controls:HamburgerMenuGlyphItem.Tag>
                             <iconPacks:PackIconMaterial Width="22"
                                                         Height="22"

src/MahApps.Metro.Samples/MahApps.Metro.Demo/MahApps.Metro.Demo.Shared/ExampleViews/HamburgerMenuSample.xaml.cs

@@ -1,6 +1,9 @@
 namespace MetroDemo.ExampleViews
 {
+    using System.Windows;
     using System.Windows.Controls;
+    using System.Windows.Input;
+    using JetBrains.Annotations;
     using MahApps.Metro.Controls;
     using MahApps.Metro.Controls.Dialogs;
 
@@ -24,10 +27,54 @@ private void HamburgerMenu_OnItemClick(object sender, ItemClickEventArgs e)
             }
         }
 
+        // Another option to handle the options menu item click
+        [UsedImplicitly]
         private async void HamburgerMenu_OnOptionsItemClick(object sender, ItemClickEventArgs e)
         {
             var menuItem = e.ClickedItem as HamburgerMenuItem;
             await this.TryFindParent<MetroWindow>().ShowMessageAsync("", $"You clicked on {menuItem.Label} button");
         }
     }
+
+    // This class can be used to avoid the following error message
+    // System.Windows.Data Error: 2 : Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=
+    // WPF doesn’t know which FrameworkElement to use to get the DataContext, because the HamburgerMenuItem doesn’t belong to the visual or logical tree of the HamburgerMenu.
+    public class BindingProxy : Freezable
+    {
+        // Using a DependencyProperty as the backing store for Data. This enables animation, styling, binding, etc...
+        public static readonly DependencyProperty DataProperty = DependencyProperty.Register("Data", typeof(object), typeof(BindingProxy), new UIPropertyMetadata(null));
+
+        public object Data
+        {
+            get { return (object)GetValue(DataProperty); }
+            set { SetValue(DataProperty, value); }
+        }
+
+        protected override Freezable CreateInstanceCore()
+        {
+            return new BindingProxy();
+        }
+    }
+
+    public static class ShowAboutCommand
+    {
+        public static readonly RoutedCommand Command = new RoutedCommand();
+
+        static ShowAboutCommand()
+        {
+            Application.Current.MainWindow.CommandBindings.Add(new CommandBinding(Command, Execute, CanExecute));
+        }
+
+        private static void CanExecute(object sender, CanExecuteRoutedEventArgs e)
+        {
+            var mainViewModel = ((MainWindow)sender).DataContext as MainWindowViewModel;
+            e.CanExecute = mainViewModel != null && mainViewModel.CanShowHamburgerAboutCommand;
+        }
+
+        private static async void Execute(object sender, ExecutedRoutedEventArgs e)
+        {
+            var menuItem = e.Parameter as HamburgerMenuItem;
+            await ((MainWindow)sender).ShowMessageAsync("", $"You clicked on {menuItem.Label} button");
+        }
+    }
 }

src/MahApps.Metro.Samples/MahApps.Metro.Demo/MahApps.Metro.Demo.Shared/MainWindowViewModel.cs

@@ -214,6 +214,22 @@ public ICommand CloseCmd
             }
         }
 
+        private bool canShowHamburgerAboutCommand = true;
+
+        public bool CanShowHamburgerAboutCommand
+        {
+            get { return this.canShowHamburgerAboutCommand; }
+            set
+            {
+                if (Equals(value, this.canShowHamburgerAboutCommand))
+                {
+                    return;
+                }
+                this.canShowHamburgerAboutCommand = value;
+                this.RaisePropertyChanged("CanShowHamburgerAboutCommand");
+            }
+        }
+
         private ICommand textBoxButtonCmd;
 
         public ICommand TextBoxButtonCmd

src/MahApps.Metro/MahApps.Metro.Shared/Controls/CommandHelpers.cs

@@ -0,0 +1,81 @@
+#if NET4
+using System;
+#endif
+using System.Security;
+using System.Windows;
+using System.Windows.Input;
+
+namespace MahApps.Metro.Controls
+{
+    internal static class CommandHelpers
+    {
+#if NET4
+        internal static readonly DependencyProperty CanExecuteChangedHandlerProperty
+            = DependencyProperty.RegisterAttached(
+                "CanExecuteChangedHandler",
+                typeof(EventHandler),
+                typeof(CommandHelpers), new FrameworkPropertyMetadata(null));
+
+        internal static EventHandler GetCanExecuteChangedHandler(DependencyObject element)
+        {
+            return (EventHandler)element.GetValue(CanExecuteChangedHandlerProperty);
+        }
+
+        internal static void SetCanExecuteChangedHandler(DependencyObject element, EventHandler value)
+        {
+            element.SetValue(CanExecuteChangedHandlerProperty, value);
+        }
+#endif
+
+        internal static bool CanExecuteCommandSource(ICommandSource commandSource)
+        {
+            var command = commandSource.Command;
+            if (command == null)
+            {
+                return false;
+            }
+            var commandParameter = commandSource.CommandParameter ?? commandSource;
+            var routedCommand = command as RoutedCommand;
+            if (routedCommand != null)
+            {
+                var target = commandSource.CommandTarget ?? commandSource as IInputElement;
+                return routedCommand.CanExecute(commandParameter, target);
+            }
+            return command.CanExecute(commandParameter);
+        }
+
+        [SecurityCritical]
+        [SecuritySafeCritical]
+        internal static void ExecuteCommandSource(ICommandSource commandSource)
+        {
+            CriticalExecuteCommandSource(commandSource);
+        }
+
+        [SecurityCritical]
+        internal static void CriticalExecuteCommandSource(ICommandSource commandSource)
+        {
+            var command = commandSource.Command;
+            if (command == null)
+            {
+                return;
+            }
+            var commandParameter = commandSource.CommandParameter ?? commandSource;
+            var routedCommand = command as RoutedCommand;
+            if (routedCommand != null)
+            {
+                var target = commandSource.CommandTarget ?? commandSource as IInputElement;
+                if (routedCommand.CanExecute(commandParameter, target))
+                {
+                    routedCommand.Execute(commandParameter, target);
+                }
+            }
+            else
+            {
+                if (command.CanExecute(commandParameter))
+                {
+                    command.Execute(commandParameter);
+                }
+            }
+        }
+    }
+}