InputBindings not firing to control menu visibility

Question

Similar to How can I toggle the main menu visibility using the Alt key in WPF? I want to control menu visibility by pressing the ALT key.

I have the following in XAML:

    <Menu Visibility="{Binding IsMenuVisable, Converter={StaticResource BooleanToVisibilityConverter}}">
        <Menu.InputBindings>
            <KeyBinding Key="LeftAlt" Command="{Binding ShowMenuCommand}"/>
            <KeyBinding Key="RightAlt" Command="{Binding ShowMenuCommand}"/>
        </Menu.InputBindings>
        <MenuItem Header="_File">
            <MenuItem Header="Open"/>
        </MenuItem>
    </Menu>

and the following in its View Model:

    private ICommand _ShowMenu;
    public ICommand ShowMenuCommand
    {
        get
        {
            if (_ShowMenu == null)
            {
                _ShowMenu = new RelayCommand(ShowMenu, CanShowMenu);
            }
            return _ShowMenu;
        }
    }
    private void ShowMenu()
    {
        IsMenuVisable = !IsMenuVisable;
    }
    private bool CanShowMenu()
    {
        return true;
    }
    private bool _IsMenuVisable = false;
    public bool IsMenuVisable
    {
        get { return _IsMenuVisable; }
        set
        {
            if (_IsMenuVisable != value)
            {
                _IsMenuVisable = value;
                OnPropertyChanged("IsMenuVisable");
            }
        }
    }

No errors are reported in the output about it not being able to match up the bindings but when I press the alt key the command is not executed. I have also tried moving the InputBindings into the window definition thinking that the menu needed focus for the InputBindings events to fire and I still do not get them to fire.

Window XAML:

<Window.Resources>
    <BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter"/>
</Window.Resources>
<Window.DataContext>
    <VM:MainWindowViewModel />
</Window.DataContext>
<Window.InputBindings>
    <KeyBinding Key="LeftAlt" Command="{Binding ShowMenuCommand}"/>
    <KeyBinding Key="RightAlt" Command="{Binding ShowMenuCommand}"/>
</Window.InputBindings>

Any thoughts and suggestions would be welcomed.

Note that the ALT keys are handled internally by the menu, that's why your keybindings don't fire. At the moment i am not sure if and how one could override the Menu-internal handling of the ALT keys... — , Aug 08 '14 at 21:00

score 0 · Answer 1 · answered Aug 08 '14 at 21:06

try using CommandBindings to bind a RouteCommand ..

<Window.CommandBindings>
    <CommandBinding Command="{x:Static local:YourView.YourCommand}" Executed="DoSomething"/>
</Window.CommandBindings>

your could bind the RouteCommand to Key input

YourCommand.InputGestures.Add( /*any key combination.*/)

score 0 · Accepted Answer · answered Aug 09 '14 at 10:30

You need to specify Modifiers as Alt in your binding to work because Alt is one of the special keys reserved for modifiers.

Change input binding to this:

<KeyBinding Modifiers="Alt" Key="LeftAlt" Command="{Binding ShowMenuCommand}"/>
<KeyBinding Modifiers="Alt" Key="RightAlt" Command="{Binding ShowMenuCommand}"/>

InputBindings not firing to control menu visibility

2 Answers2