ContainerVisual.VisualChildrenCount 属性

定义

命名空间:

System.Windows.Media

程序集:

PresentationCore.dll

获取 ContainerVisual 的子对象的数量。

protected:
 property int VisualChildrenCount { int get(); };

protected override sealed int VisualChildrenCount { get; }

member this.VisualChildrenCount : int

Protected Overrides NotOverridable ReadOnly Property VisualChildrenCount As Integer

属性值

Int32

ContainerVisual 的 VisualCollection 中的子对象的数量。

示例

下面的示例演示如何创建一个用作两DrawingVisual个 ContainerVisual 对象的父对象的 对象。 ContainerVisual添加到对象的对象必须以反向 z 顺序添加 (从下到上) ，以确保它们以正确的绘制顺序呈现。 为了正确枚举可视化树，该示例提供了 方法和 VisualChildrenCount 属性的GetVisualChild重写实现。

// Create a host visual derived from the FrameworkElement class.
// This class provides layout, event handling, and container support for
// the child visual objects.
public class MyContainerVisualHost : FrameworkElement
{
    private ContainerVisual _containerVisual;

    public MyContainerVisualHost(DrawingVisual border, DrawingVisual text)
    {
        // Create a ContainerVisual to hold DrawingVisual children.
        _containerVisual = new ContainerVisual();

        // Add children to ContainerVisual in reverse z-order (bottom to top).
        _containerVisual.Children.Add(border);
        _containerVisual.Children.Add(text);

        // Create parent-child relationship with host visual and ContainerVisual.
        this.AddVisualChild(_containerVisual);
    }

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

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

        return _containerVisual;
    }
}

' Create a host visual derived from the FrameworkElement class.
' This class provides layout, event handling, and container support for
' the child visual objects.
Public Class MyContainerVisualHost
    Inherits FrameworkElement
    Private _containerVisual As ContainerVisual

    Public Sub New(ByVal border As DrawingVisual, ByVal text As DrawingVisual)
        ' Create a ContainerVisual to hold DrawingVisual children.
        _containerVisual = New ContainerVisual()

        ' Add children to ContainerVisual in reverse z-order (bottom to top).
        _containerVisual.Children.Add(border)
        _containerVisual.Children.Add(text)

        ' Create parent-child relationship with host visual and ContainerVisual.
        Me.AddVisualChild(_containerVisual)
    End Sub

    ' Provide a required override for the VisualChildrenCount property.
    Protected Overrides ReadOnly Property VisualChildrenCount() As Integer
        Get
            Return If(_containerVisual 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 _containerVisual Is Nothing Then
            Throw New ArgumentOutOfRangeException()
        End If

        Return _containerVisual
    End Function
End Class

注解

默认情况下， ContainerVisual 没有任何子级。

继承者说明

派生自 ContainerVisual 的类必须实现 VisualChildrenCount 属性才能枚举可视子级。 派生属性必须返回 的 ContainerVisual子级数。

在此调用期间，无法修改可视化树。

另请参阅

• GetVisualChild(Int32)