How to: Create a Custom Panel Element


This example shows how to override the default layout behavior of the Panel element and create custom layout elements that are derived from Panel.

The example defines a simple custom Panel element called PlotPanel, which positions child elements according to two hard-coded x- and y-coordinates. In this example, x and y are both set to 50; therefore, all child elements are positioned at that location on the x and y axes.

To implement custom Panel behaviors, the example uses the MeasureOverride and ArrangeOverride methods. Each method returns the Size data that is necessary to position and render child elements.

    Public Class PlotPanel
        Inherits Panel
        'Override the default Measure method of Panel.

        Protected Overrides Function MeasureOverride(ByVal availableSize As System.Windows.Size) As System.Windows.Size
            Dim panelDesiredSize As Size = New Size()
            ' In our example, we just have one child. 
            ' Report that our panel requires just the size of its only child.
            For Each child As UIElement In InternalChildren
                panelDesiredSize = child.DesiredSize
            Return panelDesiredSize
        End Function
        Protected Overrides Function ArrangeOverride(ByVal finalSize As System.Windows.Size) As System.Windows.Size
            For Each child As UIElement In InternalChildren
                Dim x As Double = 50
                Dim y As Double = 50
                child.Arrange(New Rect(New System.Windows.Point(x, y), child.DesiredSize))
            Return finalSize
        End Function
    End Class

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