ContainerVisual.VisualChildrenCount Properti

Definisi

Ruang nama:

System.Windows.Media

Rakitan:

PresentationCore.dll

Mendapatkan jumlah anak untuk ContainerVisual.

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

protected override sealed int VisualChildrenCount { get; }

member this.VisualChildrenCount : int

Protected Overrides NotOverridable ReadOnly Property VisualChildrenCount As Integer

Nilai Properti

Int32

Jumlah anak-anak di VisualCollection dari ContainerVisual.

Contoh

Contoh berikut menunjukkan cara membuat ContainerVisual objek yang digunakan sebagai induk untuk dua DrawingVisual objek. Objek yang ditambahkan ke ContainerVisual objek harus ditambahkan dalam urutan z terbalik (bawah ke atas) untuk memastikan objek dirender dalam urutan gambar yang benar. Agar pohon visual dijumlahkan dengan benar, contohnya menyediakan implementasi metode dan VisualChildrenCount properti yang GetVisualChild ditimpa.

// 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

Keterangan

Secara default, ContainerVisual tidak memiliki anak.

Catatan Bagi Inheritor

Kelas yang berasal dari ContainerVisual harus mengimplementasikan VisualChildrenCount properti untuk menghitung anak-anak visual. Properti turunan harus mengembalikan jumlah anak untuk ContainerVisual.

Pohon visual tidak dapat diubah selama panggilan ini.

Lihat juga

• GetVisualChild(Int32)