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Finding an ancestor of a WPF dependency object
This is a simple snippet which helps you to find a specified parent of a given WPF dependency object somewhere in its visual tree:
(Snippet updated 2009.09.14)
/// <summary>/// Finds a parent of a given item on the visual tree./// </summary>/// <typeparam name="T">The type of the queried item.</typeparam>/// <param name="child">A direct or indirect child of the/// queried item.</param>/// <returns>The first parent item that matches the submitted/// type parameter. If not matching item can be found, a null/// reference is being returned.</returns>public static T TryFindParent<T>(this DependencyObject child) where T : DependencyObject{ //get parent item DependencyObject parentObject = GetParentObject(child); //we‘ve reached the end of the tree if (parentObject == null) return null; //check if the parent matches the type we‘re looking for T parent = parentObject as T; if (parent != null) { return parent; } else { //use recursion to proceed with next level return TryFindParent<T>(parentObject); }}/// <summary>/// This method is an alternative to WPF‘s/// <see cref="VisualTreeHelper.GetParent"/> method, which also/// supports content elements. Keep in mind that for content element,/// this method falls back to the logical tree of the element!/// </summary>/// <param name="child">The item to be processed.</param>/// <returns>The submitted item‘s parent, if available. Otherwise/// null.</returns>public static DependencyObject GetParentObject(this DependencyObject child){ if (child == null) return null; //handle content elements separately ContentElement contentElement = child as ContentElement; if (contentElement != null) { DependencyObject parent = ContentOperations.GetParent(contentElement); if (parent != null) return parent; FrameworkContentElement fce = contentElement as FrameworkContentElement; return fce != null ? fce.Parent : null; } //also try searching for parent in framework elements (such as DockPanel, etc) FrameworkElement frameworkElement = child as FrameworkElement; if (frameworkElement != null) { DependencyObject parent = frameworkElement.Parent; if (parent != null) return parent; } //if it‘s not a ContentElement/FrameworkElement, rely on VisualTreeHelper return VisualTreeHelper.GetParent(child);}
This snippet works with arbitrary dependency objects that are of Type Visual or Visual3D. So let’s say you need a reference to the Window that hosts a given Button control somewhere, all you need is this:
Button myButton = ...Window parentWindow = UIHelper.TryFindParent<Window>(myButton);
The above TryFindParent method also makes it easy to get an item at a given position. The method below performs a hit test based on a given position. If hit testing does not return the requested item (e.g. a clicked CheckBox on a tree, while you are keen on the TreeViewItem that hosts the CheckBox), the procedure delegates the lookup to TryFindParent.
This comes in very handy for mouse-related events if you just need to now what’s under your mouse pointer:
/// <summary>/// Tries to locate a given item within the visual tree,/// starting with the dependency object at a given position. /// </summary>/// <typeparam name="T">The type of the element to be found/// on the visual tree of the element at the given location.</typeparam>/// <param name="reference">The main element which is used to perform/// hit testing.</param>/// <param name="point">The position to be evaluated on the origin.</param>public static T TryFindFromPoint<T>(UIElement reference, Point point) where T:DependencyObject{ DependencyObject element = reference.InputHitTest(point) as DependencyObject; if (element == null) return null; else if (element is T) return (T)element; else return TryFindParent<T>(element);}wpf z