Visual.AddVisualChild Method

Defines the parent-child relationship between two visuals.

Namespace:  System.Windows.Media
Assembly:  PresentationCore (in PresentationCore.dll)

'Declaration
Protected Sub AddVisualChild ( _
	child As Visual _
)

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.

NoteNote

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

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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