VisualCollection.Add(Visual) Method

Definition

Namespace:

System.Windows.Media

Assembly:

PresentationCore.dll

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.