WPF Select All Focus Behavior

• Download sample - 9.6 KB

Introduction

I had a situation with a couple of PasswordBox controls, and it was frustrating because you almost never want to add to a password, especially since the actual text is obscured. I looked around for a solution. There were some custom TextBox controls to do this, but I really like to use a behavior when the impact is so minor on a control. I also found some interaction behaviors but I do not like to use these unless I have to, and I did find a behavior that only worked on TextBox controls. I therefore made my own behavior.

The Code

The following is the code for the behavior:

public class SelectAllFocusBehavior
{
    public static bool GetEnable(FrameworkElement frameworkElement)
    {
        return (bool)frameworkElement.GetValue(EnableProperty);
    }

    public static void SetEnable(FrameworkElement frameworkElement, bool value)
    {
        frameworkElement.SetValue(EnableProperty, value);
    }

    public static readonly DependencyProperty EnableProperty =
             DependencyProperty.RegisterAttached("Enable",
                typeof(bool), typeof(SelectAllFocusBehavior),
                new FrameworkPropertyMetadata(false, OnEnableChanged));

    private static void OnEnableChanged
               (DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var frameworkElement = d as FrameworkElement;
        if (frameworkElement == null) return;

        if (e.NewValue is bool == false) return;

        if ((bool)e.NewValue)
        {
            frameworkElement.GotFocus += SelectAll;
            frameworkElement.PreviewMouseDown += IgnoreMouseButton;
        }
        else
        {
            frameworkElement.GotFocus -= SelectAll;
            frameworkElement.PreviewMouseDown -= IgnoreMouseButton;
        }
    }

    private static void SelectAll(object sender, RoutedEventArgs e)
    {
        var frameworkElement = e.OriginalSource as FrameworkElement;
        if (frameworkElement is TextBox)
            ((TextBoxBase)frameworkElement).SelectAll();
        else if (frameworkElement is PasswordBox)
            ((PasswordBox)frameworkElement).SelectAll();
    }

    private static void IgnoreMouseButton
            (object sender, System.Windows.Input.MouseButtonEventArgs e)
    {
        var frameworkElement = sender as FrameworkElement;
        if (frameworkElement == null || frameworkElement.IsKeyboardFocusWithin) return;
        e.Handled = true;
        frameworkElement.Focus();
    }
}

Using the Code

This is how this behavior would be used within WPF XAML:

<TextBox Width="150"
         Margin="20"
         local:SelectAllFocusBehavior.Enable="True"
         Text="This is with Behavior" />

History

• 2018/06/20: Initial version