VisualCollection.Add(Visual) Method

Reference

Definition

Namespace:: System.Windows.Media

Assembly:: PresentationCore.dll

Important

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Appends a Visual to the end of the VisualCollection.

public:
 int Add(System::Windows::Media::Visual ^ visual);

public int Add (System.Windows.Media.Visual visual);

member this.Add : System.Windows.Media.Visual -> int

Public Function Add (visual As Visual) As Integer

Parameters

visual: Visual

The Visual to append to the VisualCollection.

Returns

Int32

The index in the collection at which visual was added.

Exceptions

ArgumentException

An ArgumentException is thrown if the Visual is a root element.

Examples

The following example shows how to create a VisualCollection and add members to it.

// 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 MyVisualHost : FrameworkElement
{
    // Create a collection of child visual objects.
    private VisualCollection _children;

    public MyVisualHost()
    {
        _children = new VisualCollection(this);
        _children.Add(CreateDrawingVisualRectangle());
        _children.Add(CreateDrawingVisualText());
        _children.Add(CreateDrawingVisualEllipses());

        // Add the event handler for MouseLeftButtonUp.
        this.MouseLeftButtonUp += new System.Windows.Input.MouseButtonEventHandler(MyVisualHost_MouseLeftButtonUp);
    }

' 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 MyVisualHost
    Inherits FrameworkElement
    ' Create a collection of child visual objects.
    Private _children As VisualCollection

    Public Sub New()
        _children = New VisualCollection(Me)
        _children.Add(CreateDrawingVisualRectangle())
        _children.Add(CreateDrawingVisualText())
        _children.Add(CreateDrawingVisualEllipses())

        ' Add the event handler for MouseLeftButtonUp.
        AddHandler MouseLeftButtonUp, AddressOf MyVisualHost_MouseLeftButtonUp
    End Sub

Note

For the complete sample, see Hit Test Using DrawingVisuals Sample.

Remarks

Adding a Visual whose value is null is permitted and does not raise an exception.

The Add method also sets up the parent-child relationship between the parent visual, which is the owner of the VisualCollection, and the child visual.

If you need greater low-level control over the underlying storage implementation of visual child objects of a custom class, consider using the AddVisualChild and RemoveVisualChild methods. When you use these methods, you must define your own storage implementation, and do not use VisualCollection.

Applies to

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