ContainerVisual.VisualChildrenCount 屬性

定義

命名空間:

System.Windows.Media

組件:

PresentationCore.dll

取得 ContainerVisual 的子系數目。

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

protected override sealed int VisualChildrenCount { get; }

member this.VisualChildrenCount : int

Protected Overrides NotOverridable ReadOnly Property VisualChildrenCount As Integer

屬性值

Int32

ContainerVisual 之 VisualCollection 中的子系數目。

範例

下列範例示範如何建立物件，該物件會當做兩 DrawingVisual 個 ContainerVisual 物件的父系使用。 新增至 ContainerVisual 物件的物件必須以反向迭置順序新增， (由下到上) ，以確保它們以正確的繪圖順序呈現。 為了讓視覺化樹狀結構正確列舉，此範例會提供方法與 VisualChildrenCount 屬性的 GetVisualChild 覆寫實作。

// 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

備註

根據預設，沒有 ContainerVisual 任何子系。

給繼承者的注意事項

衍生自 ContainerVisual 的 VisualChildrenCount 類別必須實作 屬性，才能列舉視覺子系。 衍生屬性必須傳回 的子 ContainerVisual 係數目。

此呼叫期間無法修改視覺化樹狀結構。

另請參閱

• GetVisualChild(Int32)