Why doesn't setting MenuItem.InputGestureText cause the MenuItem to activate when I perform the input gesture?

Question

I want to implement Keyboard shortcuts for a MenuItem. I have used the code below:

Answer 1

The best way to do this is to make a Command, and associate the InputGesture with that command:

public static class Commands
{
    public static readonly RoutedCommand CreateNew = new RoutedCommand("New", typeof(Commands));

    static Commands()
    {
        SomeCommand.InputGestures.Add(new KeyGesture(Key.N, ModifierKeys.Control));
    }
}

...

// Wherever you want to create the MenuItem. "local" should be the namespace that
// you delcared "Commands" in.
<MenuItem Header="_New" Command="{x:Static local:Commands.CreateNew}">

...

// Wherever you want to process the command. I am assuming you want to do it in your 
// main window, but you can do it anywhere in the route between your main window and 
// the menu item.
<Window.CommandBindings>
    <CommandBinding Command="{x:Static local:Commands.CreateNew}"> Executed="CreateNew_Executed" />
</Window.CommandBindings>

...

// In the code behind for your main window (or whichever file you put the above XAML in)
private void CreateNew(object sender, ExecutedRoutedEventArgs e)
{
    ...
}

If you really just want a "New" command, you can skip creating the RoutedCommand and InputGesture, because that command is already created for you:

<MenuItem Header="_New" Command="New">

...

<Window.CommandBindings>
    <CommandBinding Command="New" Executed="New_Executed" />
</Window.CommandBindings>

...

private void New_Executed(object sender, ExecutedRoutedEventArgs e)
{
    ...
}

Answer 2

It is quite explicit in the documentation for the property:

This property does not associate the input gesture with the menu item; it simply adds text to the menu item. The application must handle the user's input to carry out the action. For information on how to associate a command with a menu item, see Command.

Answer 3

One solution that doesn't involve commands and bindings is to override the owning Window's OnKeyDown method and search a menu item that has a KeyGesture that matches the keyboard event.

Here is the code for the Window's OnKeyDown override:

protected override void OnKeyDown(KeyEventArgs e)
{
    base.OnKeyDown(e);

    // here I suppose the window's menu is named "MainMenu"
    MainMenu.RaiseMenuItemClickOnKeyGesture(e);
}

And here is the utility code that matches a menu item with the keyboard event:

    public static void RaiseMenuItemClickOnKeyGesture(this ItemsControl control, KeyEventArgs args) => RaiseMenuItemClickOnKeyGesture(control, args, true);
    public static void RaiseMenuItemClickOnKeyGesture(this ItemsControl control, KeyEventArgs args, bool throwOnError)
    {
        if (args == null)
            throw new ArgumentNullException(nameof(args));

        if (control == null)
            return;

        var kgc = new KeyGestureConverter();
        foreach (var item in control.Items.OfType<MenuItem>())
        {
            if (!string.IsNullOrWhiteSpace(item.InputGestureText))
            {
                KeyGesture gesture = null;
                if (throwOnError)
                {
                    gesture = kgc.ConvertFrom(item.InputGestureText) as KeyGesture;
                }
                else
                {
                    try
                    {
                        gesture = kgc.ConvertFrom(item.InputGestureText) as KeyGesture;
                    }
                    catch
                    {
                    }
                }

                if (gesture != null && gesture.Matches(null, args))
                {
                    item.RaiseEvent(new RoutedEventArgs(MenuItem.ClickEvent));
                    args.Handled = true;
                    return;
                }
            }

            RaiseMenuItemClickOnKeyGesture(item, args, throwOnError);
            if (args.Handled)
                return;
        }
    }