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)

 

/// 
/// Finds a parent of a given item on the visual tree./// 
/// 
     
      The type of the queried item.
     /// A direct or indirect child of the/// queried item. /// 
     
      The first parent item that matches the submitted /// type parameter. If not matching item can be found, a null /// reference is being returned.
      public static T TryFindParent
     
      (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
      
       (parentObject); } } /// 
       
 /// This method is an alternative to WPF's /// 
         method, which also /// supports content elements. Keep in mind that for content element, /// this method falls back to the logical tree of the element! /// 
 /// 
       The item to be processed. /// 
       
        The submitted item's parent, if available. Otherwise /// null.
        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
     
      (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:

/// 
/// Tries to locate a given item within the visual tree,/// starting with the dependency object at a given position. /// 
/// 
     
      The type of the element to be found/// on the visual tree of the element at the given location.
      /// The main element which is used to perform /// hit testing. /// The position to be evaluated on the origin. public static T TryFindFromPoint
     
      (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
      
       (element); }