Visual.AddVisualChild Method (Visual)
Defines the parent-child relationship between two visuals.
Assembly: PresentationCore (in PresentationCore.dll)
Parameters
- child
-
Type:
System.Windows.Media.Visual
The child visual object to add to parent visual.
The AddVisualChild method sets up the parent-child relationship between two visual objects. This method must be used when you need greater low-level control over the underlying storage implementation of visual child objects. VisualCollection can be used as a default implementation for storing child objects.
The following example shows how to define custom storage requirements for a visual child. The example uses the AddVisualChild and RemoveVisualChild methods to sets up the parent-child relationship between the parent visual and child. In order for the visual tree to be enumerated correctly, the example provides overridden implementations of the GetVisualChild method and VisualChildrenCount property.
Note |
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Although it is possible to use VisualCollection to create parent-child relationships between visual objects, it is more efficient to provide your own custom storage implementation when only one child is linked to a parent. |
' Create a host visual derived from the FrameworkElement class. ' This class provides layout, event handling, and container support for ' the child visual object. Public Class MyVisualHost Inherits FrameworkElement Private _child As DrawingVisual Public Sub New(ByVal drawingVisual As DrawingVisual) _child = drawingVisual Me.AddVisualChild(_child) End Sub Public Property Child() As DrawingVisual Get Return _child End Get Set(ByVal value As DrawingVisual) If _child IsNot value Then Me.RemoveVisualChild(_child) _child = value Me.AddVisualChild(_child) End If End Set End Property ' Provide a required override for the VisualChildrenCount property. Protected Overrides ReadOnly Property VisualChildrenCount() As Integer Get Return If(_child Is Nothing, 0, 1) End Get End Property ' Provide a required override for the GetVisualChild method. Protected Overrides Function GetVisualChild(ByVal index As Integer) As Visual If _child Is Nothing Then Throw New ArgumentOutOfRangeException() End If Return _child End Function
Available since 3.0
