PointAnimation.By Property

Gets or sets the total amount by which the animation changes its starting value.

Namespace:  System.Windows.Media.Animation
Assembly:  PresentationCore (in PresentationCore.dll)
XMLNS for XAML: http://schemas.microsoft.com/winfx/2006/xaml/presentation, http://schemas.microsoft.com/netfx/2007/xaml/presentation

public Nullable<Point> By { get; set; }
<object>  <object.By>    <Point />  </object.By></object>
<object By="Point"/>- or -<object By="{x:Null Markup Extension}"/>

Property Value

Type: System.Nullable<Point>
The total amount by which the animation changes its starting value. The default value is null.

Identifier field

ByProperty

Metadata properties set to true

None

Use the By property when you want to animate a value "by" a certain amount, rather than specifying a starting or ending value. You may also use the By property with the From property. The following table summarizes how the From, To, and By properties may be used together or separately to determine an animation's target values.

Properties Specified

Resulting Behavior

From

The animation progresses from the value specified by the From property to the base value of the property being animated or to a previous animation's output value, depending on how the previous animation is configured.

From and To

The animation progresses from the value specified by the From property to the value specified by the To property.

From and By

The animation progresses from the value specified by the From property to the value specified by the sum of the From and By properties.

To

The animation progresses from the animated property's base value or a previous animation's output value to the value specified by the To property.

By

The animation progresses from the base value of the property being animated or a previous animation's output value to the sum of that value and the value specified by the By property.

Note   If you set both the To and By properties, the To property takes precedence and the By property is ignored.

To use other interpolation methods or animate between more than two target values, use a PointAnimationUsingKeyFrames object.

This example shows how to use the PointAnimation class to animate an object along a Path.

The following example moves an ellipse along a Path from one point on the screen to another. The example animates the position of an EllipseGeometry by using PointAnimation to animate the Center property.


using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Shapes;
using System.Windows.Media.Animation;
using System.Windows.Media;

namespace SDKSamples
{
    // This example shows how to use PointAnimation to animate the
    // position of an ellipse by animating the Center property of an 
    // EllipseGeometry. PointAnimation is used because the Center property
    // takes a Point value.
    public class PointAnimationExample : Page
    {
        public PointAnimationExample()
        {

            // Create a NameScope for this page so that
            // Storyboards can be used.
            NameScope.SetNameScope(this, new NameScope());

            EllipseGeometry myEllipseGeometry = new EllipseGeometry();
            myEllipseGeometry.Center = new Point(200, 100);
            myEllipseGeometry.RadiusX = 15;
            myEllipseGeometry.RadiusY = 15;

            // Assign the EllipseGeometry a name so that
            // it can be targeted by a Storyboard.
            this.RegisterName(
                "MyAnimatedEllipseGeometry", myEllipseGeometry);

            Path myPath = new Path();
            myPath.Fill = Brushes.Blue;
            myPath.Margin = new Thickness(15);
            myPath.Data = myEllipseGeometry;

            PointAnimation myPointAnimation = new PointAnimation();
            myPointAnimation.Duration = TimeSpan.FromSeconds(2);

            // Set the animation to repeat forever. 
            myPointAnimation.RepeatBehavior = RepeatBehavior.Forever;

            // Set the From and To properties of the animation.
            myPointAnimation.From = new Point(200, 100);
            myPointAnimation.To = new Point(450, 250);

            // Set the animation to target the Center property
            // of the object named "MyAnimatedEllipseGeometry."
            Storyboard.SetTargetName(myPointAnimation, "MyAnimatedEllipseGeometry");
            Storyboard.SetTargetProperty(
                myPointAnimation, new PropertyPath(EllipseGeometry.CenterProperty));

            // Create a storyboard to apply the animation.
            Storyboard ellipseStoryboard = new Storyboard();
            ellipseStoryboard.Children.Add(myPointAnimation);

            // Start the storyboard when the Path loads.
            myPath.Loaded += delegate(object sender, RoutedEventArgs e)
            {
                ellipseStoryboard.Begin(this);
            };

            Canvas containerCanvas = new Canvas();
            containerCanvas.Children.Add(myPath);

            Content = containerCanvas;
        }

    }
}



<!-- This example shows how to use PointAnimation to animate the
position of an ellipse by animating the Center property of an 
EllipseGeometry. PointAnimation is used because the Center property
takes a Point value. -->
<Page  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Canvas>
      <Path Fill="Blue" Margin="15,15,15,15">
        <Path.Data>

          <!-- Describes an ellipse. -->
          <EllipseGeometry x:Name="MyAnimatedEllipseGeometry"
            Center="200,100" RadiusX="15" RadiusY="15" />
        </Path.Data>
        <Path.Triggers>
          <EventTrigger RoutedEvent="Path.Loaded">
            <BeginStoryboard Name="MyBeginStoryboard">
              <Storyboard>

                <!-- Animate the Center property so that the ellipse animates from 
                one point on the screen to another. -->
                <PointAnimation
                Storyboard.TargetProperty="Center"
                Storyboard.TargetName="MyAnimatedEllipseGeometry"
                Duration="0:0:2" From="200,100" To="450,250" RepeatBehavior="Forever" />
              </Storyboard>
            </BeginStoryboard>
          </EventTrigger>
        </Path.Triggers>
      </Path>
    </Canvas>
</Page>


More Code

How to: Control an Animation using From, To, and ByA "From/To/By" or "basic animation" creates a transition between two target values (see Animation Overview for an introduction to different types of animations). To set the target values of a basic animation, use its From, To, and By properties. The following table summarizes how the From, To, and By properties may be used together or separately to determine an animation's target values.

.NET Framework

Supported in: 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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