FrameworkElement.AddLogicalChild Method
Assembly: PresentationFramework (in presentationframework.dll)
'Declaration Protected Friend Sub AddLogicalChild ( _ child As Object _ ) 'Usage Dim child As Object Me.AddLogicalChild(child)
protected void AddLogicalChild ( Object child )
protected internal function AddLogicalChild ( child : Object )
You cannot use methods in XAML.
Parameters
- child
Child element to be added.
Use this method for the implementation of collections on objects that represent logical child elements of an element. Collection maintenance for child element collections might be done in property getters or setters, class handling of Changed events, constructors, or within the collection types themselves.
For control authors, manipulating the logical tree at this level is not the recommended practice, unless none of the content models for available base control classes are appropriate for your control scenario. Consider subclassing at the level of ContentControl, ItemsControl, and HeaderedItemsControl. These classes provide a content model with particular enforcement of logical tree child elements through dedicated APIs, as well as support for other features typically desirable in a WPF control such as styling through templates. For more information on how to use LogicalChildren and AddLogicalChild, see Logical Tree Overview.
AddLogicalChild may raise an exception if called at a time when the logical tree is being iterated by another process.
The following example implements a Child property on a custom FrameworkElement that does its own visual layer implementation. The property setter is designed so that if the value changes, the old value is removed from the logical tree, as well as a class-specific visual collection. The property value is cached, and then the new value is added to both the logical tree and the custom visual collection.
public virtual UIElement Child { get { return _child; } set { if (_child != value) { //need to remove old element from logical tree if (_child != null) { OnDetachChild(_child); RemoveLogicalChild(_child); } _vc.Clear(); if (value != null) { //add to visual _vc.Add(value); //add to logical AddLogicalChild(value); } //always add the overlay child back into the visual tree if its set if (_overlayVisual != null) _vc.Add(_overlayVisual); //cache the new child _child = value; //notify derived types of the new child if (value != null) OnAttachChild(_child); InvalidateMeasure(); } } }
Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.