private static void AttachToLoadedEvent(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs args)
{
if (!(dependencyObject is TextBox textBox))
{
return;
}
var enabled = args.NewValue != null && (bool)args.NewValue;
if (enabled)
{
if (textBox.IsLoaded)
{
// Directly set the focus.
TextBoxHelper.SetFocus(textBox, new RoutedEventArgs());
}
else
{
// Apply a handler to the loaded event.
TextBoxHelper.AddHandlers(textBox);
}
}
else
{
TextBoxHelper.RemoveHandlers(textBox);
}
}
private static void SetFocus(object sender, RoutedEventArgs args)
{
// Remove this handler.
TextBoxHelper.RemoveHandlers(sender);
// Cast the framework element to an input element.
if (!(sender is IInputElement inputElement))
{
return;
}
// Set the focus.
Application.Current.Dispatcher.BeginInvoke
(
(Action) delegate
{
System.Windows.Input.Keyboard.Focus(inputElement);
}, System.Windows.Threading.DispatcherPriority.Render
);
}
private static void RemoveHandlers(object sender) => TextBoxHelper.RemoveHandlers(sender, null);
