绑定命令时WPF MenuItem变灰

Question

I'm trying to hook up commands to context menu items in a TaskbarIcon but everytime I do, they become grayed out. Here's the XAML:

<ResourceDictionary
                xmlns:local="clr-namespace:Stickie.StickieNotes.WPFGUI"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:tb="http://www.hardcodet.net/taskbar"
>
<!-- Globally declared notify icon -->
<tb:TaskbarIcon x:Key="MyNotifyIcon">
    <tb:TaskbarIcon.ContextMenu>
        <ContextMenu>
            <MenuItem Header="Open Settings" Command="local:App.OpenSettingsCommand" 
                      CommandTarget="{Binding Path=PlacementTarget, RelativeSource={RelativeSource AncestorType={x:Type ContextMenu}}}"/>
            <MenuItem Header="New Note"/>
            <MenuItem Header="Exit" Command="local:App.ExitApplicationCommand"
                      CommandTarget="{Binding Path=PlacementTarget, RelativeSource={RelativeSource AncestorType={x:Type ContextMenu}}}"/>
        </ContextMenu>
    </tb:TaskbarIcon.ContextMenu>
</tb:TaskbarIcon>

And my backing CS:

namespace Stickie.StickieNotes.WPFGUI
{
    /// <summary>
    /// Interaction logic for App.xaml
    /// </summary>
    public partial class App : Application
    {
        static App()
        {
            initializeCommands();
        }
        static void initializeCommands()
        {
            Type ownerType = typeof (App);
            OpenSettingsCommand = new RoutedCommand("OpenSettings", ownerType);
            ExitApplicationCommand = new RoutedCommand("ExitApplication", ownerType);
            CommandBinding openSettings = new CommandBinding(OpenSettingsCommand, OpenSettingsExecuted, OpenSettingCanExecute);
            CommandBinding exitApplication = new CommandBinding(ExitApplicationCommand, ExitApplicationExecuted, ExitApplicationCanExecute);
            CommandManager.RegisterClassCommandBinding(ownerType,openSettings);
            CommandManager.RegisterClassCommandBinding(ownerType,exitApplication);
        }
        public static RoutedCommand OpenSettingsCommand;
        public static RoutedCommand ExitApplicationCommand;

        private static void ExitApplicationCanExecute(object sender, CanExecuteRoutedEventArgs e)
        {
            e.CanExecute = true;
        }

        private static void OpenSettingCanExecute(object sender, CanExecuteRoutedEventArgs e)
        {
            e.CanExecute = true;
        }

        private static void ExitApplicationExecuted(object sender, ExecutedRoutedEventArgs e)
        {
            Application.Current.Shutdown(0);
        }

        private static void OpenSettingsExecuted(object sender, ExecutedRoutedEventArgs e)
        {
            if (Application.Current.MainWindow != null)
            {
                Application.Current.MainWindow.Show();
            }
        }
    }
}

I've been playing around with it and looking around a ton but I can't seem to get it to work. Does anyone have a possible solution?

Answer 1

From this article :

ContextMenus are separate windows with their own VisualTree and LogicalTree. [...] the CommandManager searches for CommandBindings within the current focus scope. If the current focus scope has no command binding, it transfers the focus scope to the parent focus scope. When you startup your application the focus scope is not set. You can check this by calling FocusManager.GetFocusedElement(this) and you will receive null.

The simplest solution is to initially set the logical focus:

public Window1()
{
    InitializeComponent();

    // Set the logical focus to the window
    Focus();
}

Another solution is to manually bind the CommandTarget to the parent ContextMenu.

<MenuItem Header="Cut" Command="Cut" CommandTarget="
          {Binding Path=PlacementTarget, 
          RelativeSource={RelativeSource FindAncestor, 
          AncestorType={x:Type ContextMenu}}}"/>