WPF attached behavior triggering after button click

Question

I have the following class / behavior which is being called on button click event. The issue is that it gets called after button_click event. How to call it before button click event? The below mentioned style is defined in App.xaml for global usage

XAML:

<Style TargetType="Button">
        <Setter Property="local:DefaultButtonBehaviour.DefaultButton" Value="True" />
</Style>

CODE:

public static class DefaultButtonBehaviour
{
    /// 1. This is the boolean attached property with its getter and setter:
    public static readonly DependencyProperty DefaultButtonProperty =
        DependencyProperty.RegisterAttached
        (
            "DefaultButton",
            typeof(bool),
            typeof(DefaultButtonBehaviour),
            new UIPropertyMetadata(false, OnDefaultButtonPropertyChanged)
        );
    public static bool GetDefaultButton(DependencyObject obj)
    {
        return (bool)obj.GetValue(DefaultButtonProperty);
    }
    private static void SetDefaultButton(DependencyObject obj, bool value)
    {
        obj.SetValue(DefaultButtonProperty, value);
    }

    /// 2. This is the change event of our attached property value:
    ///     * We get in the first parameter the dependency object to which the attached behavior was attached
    ///     * We get in the second parameter the value of the attached behavior.
    ///     * The implementation of the behavior is to check if we are attached to a textBox, and if so and the value of the behavior
    ///       is true, hook to the PreviewGotKeyboardFocus of the textbox.
    private static void OnDefaultButtonPropertyChanged(DependencyObject dpo, DependencyPropertyChangedEventArgs args)
    {
        ButtonBase button = dpo as ButtonBase;
        if (button != null)
        {
            if ((bool)args.NewValue)
            {
                button.Click += OnDefaultButtonClick;
            }
            else
            {
                button.Click -= OnDefaultButtonClick; ;
            }
        }
    }

    private static void OnDefaultButtonClick(object sender, RoutedEventArgs e)
    {
        ButtonBase btn = (ButtonBase)sender;
        DependencyObject focusScope = FocusManager.GetFocusScope(btn);
        FocusManager.SetFocusedElement(focusScope, btn);
        Keyboard.Focus(btn);
    }

}

Answer 1

If I am following the question properly, you could approach this by wiring up the Preview events. Hook into PreviewMouseDown and PreviewKeyDown (so you can handle the case where the user uses the return key to activate the button).