/// <summary>
/// When overridden in a derived class, returns a <see cref="T:System.Windows.DataTemplate" /> based on custom logic.
/// </summary>
/// <param name="item">The data object for which to select the template.</param>
/// <param name="container">The data-bound object.</param>
/// <returns>
/// Returns a <see cref="T:System.Windows.DataTemplate" /> or null. The default value is null.
/// </returns>
public override DataTemplate SelectTemplate(object item, DependencyObject container)
{
if ((item == null) || (container == null))
return null;
var frameworkElement = container.AncestorsAndSelf().OfType<FrameworkElement>().FirstOrDefault();
if (frameworkElement == null)
return null;
var key = DataTemplateManager.CreateKey(item.GetType(), Role);
return (frameworkElement.TryFindResource(key) as DataTemplate) ?? FallbackValue;
}
/// <summary>
/// Returns a collection containing this element and all ancestor elements
/// which match the given type.
/// </summary>
public static IEnumerable <DependencyObject> AncestorsAndSelf <T>(this DependencyObject item)
{
return(item.AncestorsAndSelf().Where(i => i is T));
}
/// <summary>
/// Invoked when the HorizontalOffset attached property changes
/// </summary>
private static void OnHorizontalOffsetPropertyChanged(DependencyObject d,
DependencyPropertyChangedEventArgs e)
{
ScrollViewer sv = d.AncestorsAndSelf<ScrollViewer>().FirstOrDefault() as ScrollViewer;
if (sv == null)
return;
// check whether we have a reference to the vertical scrollbar
if (sv.GetValue(horizontalScrollBarProperty) == null)
{
// if not, handle LayoutUpdated, which will be invoked after the
// template is applied and extract the scrollbar
sv.LayoutUpdated += (s, ev) =>
{
if (sv.GetValue(horizontalScrollBarProperty) == null)
{
GetScrollBarsForScrollViewer(sv);
}
};
}
else
{
// update the scrollviewer offset
sv.ScrollToHorizontalOffset((double)e.NewValue);
}
}
