FrameworkElement.ActualWidth Property

Reference

Definition

Namespace:: System.Windows

Assembly:: PresentationFramework.dll

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Gets the rendered width of this element.

public:
 property double ActualWidth { double get(); };

public double ActualWidth { get; }

member this.ActualWidth : double

Public ReadOnly Property ActualWidth As Double

Property Value

Double

The element's width, as a value in device-independent units (1/96th inch per unit). The default value is 0 (zero).

Examples

The following example displays various width properties.

private void changeWidth(object sender, SelectionChangedEventArgs args)
{
    ListBoxItem li = ((sender as ListBox).SelectedItem as ListBoxItem);
    Double sz1 = Double.Parse(li.Content.ToString());
    rect1.Width = sz1;
    rect1.UpdateLayout();
    txt1.Text = "ActualWidth is set to " + rect1.ActualWidth;
    txt2.Text = "Width is set to " + rect1.Width;
    txt3.Text = "MinWidth is set to " + rect1.MinWidth;
    txt4.Text = "MaxWidth is set to " + rect1.MaxWidth;
}
private void changeMinWidth(object sender, SelectionChangedEventArgs args)
{
    ListBoxItem li = ((sender as ListBox).SelectedItem as ListBoxItem);
    Double sz1 = Double.Parse(li.Content.ToString());
    rect1.MinWidth = sz1;
    rect1.UpdateLayout();
    txt1.Text = "ActualWidth is set to " + rect1.ActualWidth;
    txt2.Text = "Width is set to " + rect1.Width;
    txt3.Text = "MinWidth is set to " + rect1.MinWidth;
    txt4.Text = "MaxWidth is set to " + rect1.MaxWidth;
}
private void changeMaxWidth(object sender, SelectionChangedEventArgs args)
{
    ListBoxItem li = ((sender as ListBox).SelectedItem as ListBoxItem);
    Double sz1 = Double.Parse(li.Content.ToString());
    rect1.MaxWidth = sz1;
    rect1.UpdateLayout();
    txt1.Text = "ActualWidth is set to " + rect1.ActualWidth;
    txt2.Text = "Width is set to " + rect1.Width;
    txt3.Text = "MinWidth is set to " + rect1.MinWidth;
    txt4.Text = "MaxWidth is set to " + rect1.MaxWidth;
}

Private Sub changeWidth(ByVal sender As Object, ByVal args As SelectionChangedEventArgs)
    Dim li As ListBoxItem = CType(CType(sender, ListBox).SelectedItem, ListBoxItem)
    Dim sz1 As Double = Double.Parse(li.Content.ToString())
    rect1.Width = sz1
    rect1.UpdateLayout()
    txt1.Text = "ActualWidth is set to " + rect1.ActualWidth.ToString
    txt2.Text = "Width is set to " + rect1.Width.ToString
    txt3.Text = "MinWidth is set to " + rect1.MinWidth.ToString
    txt4.Text = "MaxWidth is set to " + rect1.MaxWidth.ToString
End Sub
Private Sub changeMinWidth(ByVal sender As Object, ByVal args As SelectionChangedEventArgs)

    Dim li As ListBoxItem = CType(CType(sender, ListBox).SelectedItem, ListBoxItem)
    Dim sz1 As Double = Double.Parse(li.Content.ToString())
    rect1.MinWidth = sz1
    rect1.UpdateLayout()
    txt1.Text = "ActualWidth is set to " + rect1.ActualWidth.ToString
    txt2.Text = "Width is set to " + rect1.Width.ToString
    txt3.Text = "MinWidth is set to " + rect1.MinWidth.ToString
    txt4.Text = "MaxWidth is set to " + rect1.MaxWidth.ToString
End Sub
Private Sub changeMaxWidth(ByVal sender As Object, ByVal args As SelectionChangedEventArgs)

    Dim li As ListBoxItem = CType(CType(sender, ListBox).SelectedItem, ListBoxItem)
    Dim sz1 As Double = Double.Parse(li.Content.ToString())
    rect1.MaxWidth = sz1
    rect1.UpdateLayout()
    txt1.Text = "ActualWidth is set to " + rect1.ActualWidth.ToString
    txt2.Text = "Width is set to " + rect1.Width.ToString
    txt3.Text = "MinWidth is set to " + rect1.MinWidth.ToString
    txt4.Text = "MaxWidth is set to " + rect1.MaxWidth.ToString
End Sub

Remarks

This property is a calculated value based on other width inputs, and the layout system. The value is set by the layout system itself, based on an actual rendering pass, and may therefore lag slightly behind the set value of properties such as Width that are the basis of the input change.

Because ActualWidth is a calculated value, you should be aware that there could be multiple or incremental reported changes to it as a result of various operations by the layout system. The layout system may be calculating required measure space for child elements, constraints by the parent element, and so on.

Although you cannot set this property from XAML, you can base a Trigger upon its value in a style.

Dependency Property Information

Item	Value
Identifier field	ActualWidthProperty
Metadata properties set to `true`	None

Applies to

通过