Visual.AddVisualChild(Visual) Method

protected:
 void AddVisualChild(System::Windows::Media::Visual ^ child);

protected void AddVisualChild (System.Windows.Media.Visual child);

member this.AddVisualChild : System.Windows.Media.Visual -> unit

Protected Sub AddVisualChild (child As Visual)

Parameters

Examples

下面的示例演示如何为视觉对象定义自定义存储要求。The following example shows how to define custom storage requirements for a visual child. 该示例使用 AddVisualChild 和 RemoveVisualChild 方法来设置父视觉对象与 child之间的父子关系。The example uses the AddVisualChild and RemoveVisualChild methods to sets up the parent-child relationship between the parent visual and child. 为了正确枚举可视化树，该示例提供 GetVisualChild 方法的重写实现和 VisualChildrenCount 属性。In order for the visual tree to be enumerated correctly, the example provides overridden implementations of the GetVisualChild method and VisualChildrenCount property.

// 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 : FrameworkElement
{
    private DrawingVisual _child;

    public MyVisualHost(DrawingVisual drawingVisual)
    {
        _child = drawingVisual;
        this.AddVisualChild(_child);
    }

    public DrawingVisual Child
    {
        get
        {
            return _child;
        }

        set
        {
            if (_child != value)
            {
                this.RemoveVisualChild(_child);
                _child = value;
                this.AddVisualChild(_child);
            }
        }
    }

    // Provide a required override for the VisualChildrenCount property.
    protected override int VisualChildrenCount
    {
        get { return _child == null ? 0 : 1; }
    }

    // Provide a required override for the GetVisualChild method.
    protected override Visual GetVisualChild(int index)
    {
        if (_child == null)
        {
            throw new ArgumentOutOfRangeException();
        }

        return _child;
    }

' 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

Remarks

AddVisualChild 方法设置两个可视对象之间的父子关系。The AddVisualChild method sets up the parent-child relationship between two visual objects. 如果需要对可视子对象的基础存储实现进行更高级别的控制，则必须使用此方法。This method must be used when you need greater low-level control over the underlying storage implementation of visual child objects. VisualCollection 可用作存储子对象的默认实现。VisualCollection can be used as a default implementation for storing child objects.

Applies to

See also

• VisualCollection