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UIElement.DesiredSize Property

Gets the size that this element computed during the measure pass of the layout process.

Namespace: System.Windows
Assembly: PresentationCore (in presentationcore.dll)
XML Namespace:  http://schemas.microsoft.com/winfx/2006/xaml/presentation

public Size DesiredSize { get; }
/** @property */
public Size get_DesiredSize ()

public function get DesiredSize () : Size

You cannot use this property in XAML.

Property Value

The computed size, which becomes the desired size for the arrange pass.

The value returned by this property will only be a valid measurement if the value of the IsMeasureValid property is true.

DesiredSize is typically checked as one of the measurement factors when you implement layout behavior overrides such as ArrangeOverride, MeasureOverride or OnRender. Depending on the scenario, DesiredSize might be fully respected by your implementation logic, constraints on DesiredSize might be applied, and such constraints might also change other characteristics of either the parent element or child element. For example, a control that supports scrollable regions (but chooses not to derive from the WPF framework-level controls that already enable scrollable regions) could compare available size to DesiredSize. The control could then set an internal state that enabled scrollbars in the UI for that control. Or, DesiredSize could potentially also be ignored in certain scenarios.

The following example shows how a custom adorner uses the DesiredSize value in order to create and size the rectangle graphic that defines the adorner, as part of its OnRender implementation.

protected override void OnRender(DrawingContext drawingContext)
{
  // Get a rectangle that represents the desired size of the rendered element
  // after the rendering pass.  This will be used to draw at the corners of the 
  // adorned element.
  Rect adornedElementRect = new Rect(this.AdornedElement.DesiredSize);

  // Some arbitrary drawing implements.
  SolidColorBrush renderBrush = new SolidColorBrush(Colors.Green);
  renderBrush.Opacity = 0.2;
  Pen renderPen = new Pen(new SolidColorBrush(Colors.Navy), 1.5);
  double renderRadius = 5.0;

  // Just draw a circle at each corner.
  drawingContext.DrawEllipse(renderBrush, renderPen, adornedElementRect.TopLeft, renderRadius, renderRadius);
  drawingContext.DrawEllipse(renderBrush, renderPen, adornedElementRect.TopRight, renderRadius, renderRadius);
  drawingContext.DrawEllipse(renderBrush, renderPen, adornedElementRect.BottomLeft, renderRadius, renderRadius);
  drawingContext.DrawEllipse(renderBrush, renderPen, adornedElementRect.BottomRight, renderRadius, renderRadius);
}

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0
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