Hide ToggleButton on WPF Expander by binding

Question

I am trying to dynamically hide the Toggle button on an Expander using the property on my ViewModel set to Visibility. At least that's my thought. Is there a way to simply change this setting in a ToggleButton control without having to do the WHOLE Toggle button template in my xaml for this?

Answer 1

You can use the Loaded event for Expander and configure Binding in the event handler, or if you want to use the reusable path without the code behind, you can use the attached behavior.

The attached behavior finds the ToggleButton inside the Template and sets the Binding to the attached ToggleButtonVisibility property.

An example application is downloaded here: ExpanderToggleButtonVisibilityTest.zip

Use it like this:

 <Expander Name="expander" behaviors:ExpanderBehavior.BindToggleButtonVisibility="True" behaviors:ExpanderBehavior.ToggleButtonVisibility="{Binding YourVisibilityProperty}" .../> 

Expanderbehavior

 public class ExpanderBehavior { public static DependencyProperty BindToggleButtonVisibilityProperty = DependencyProperty.RegisterAttached("BindToggleButtonVisibility", typeof(bool), typeof(ExpanderBehavior), new PropertyMetadata(false, OnBindToggleButtonVisibilityChanged)); public static bool GetBindToggleButtonVisibility(Expander expander) { return (bool)expander.GetValue(BindToggleButtonVisibilityProperty); } public static void SetBindToggleButtonVisibility(Expander expander, bool value) { expander.SetValue(BindToggleButtonVisibilityProperty, value); } private static void OnBindToggleButtonVisibilityChanged(DependencyObject target, DependencyPropertyChangedEventArgs e) { Expander expander = target as Expander; if (expander.IsLoaded == true) { BindToggleButtonVisibility(expander); } else { RoutedEventHandler loadedEventHandler = null; loadedEventHandler = new RoutedEventHandler(delegate { BindToggleButtonVisibility(expander); expander.Loaded -= loadedEventHandler; }); expander.Loaded += loadedEventHandler; } } private static void BindToggleButtonVisibility(Expander expander) { ToggleButton headerSite = expander.Template.FindName("HeaderSite", expander) as ToggleButton; if (headerSite != null) { Binding visibilityBinding = new Binding { Source = expander, Path = new PropertyPath(ToggleButtonVisibilityProperty) }; headerSite.SetBinding(ToggleButton.VisibilityProperty, visibilityBinding); } } #region ToggleButtonVisibilityProperty public static DependencyProperty ToggleButtonVisibilityProperty = DependencyProperty.RegisterAttached("ToggleButtonVisibility", typeof(Visibility), typeof(ExpanderBehavior), new PropertyMetadata(Visibility.Visible)); public static Visibility GetToggleButtonVisibility(Expander expander) { return (Visibility)expander.GetValue(ToggleButtonVisibilityProperty); } public static void SetToggleButtonVisibility(Expander expander, Visibility value) { expander.SetValue(ToggleButtonVisibilityProperty, value); } #endregion // ToggleButtonVisibilityProperty }