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Pooja PoojariandAndy De George
692293bda8
* Updated H2 and column headers. * Metadata update. * Minor edits. * Apply suggestions from code review Co-authored-by: Andy (Steve) De George <[email protected]>
54 lines
3.1 KiB
Markdown
54 lines
3.1 KiB
Markdown
---
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title: "How to: Receive Notification When a Clock's State Changes"
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description: Learn how to receive notification when a Clock's state changes.
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ms.date: "03/30/2017"
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ms.custom: devdivchpfy22
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dev_langs:
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- "csharp"
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- "vb"
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helpviewer_keywords:
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- "clocks [WPF], notification of state changes"
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- "notifications [WPF], clocks' state changes"
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ms.assetid: ecb10fc9-d0c2-45c3-b0a1-7b11baa733da
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---
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# How to: Receive Notification When a Clock's State Changes
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A clock's <xref:System.Windows.Media.Animation.Clock.CurrentStateInvalidated> event occurs when its <xref:System.Windows.Media.Animation.Clock.CurrentState%2A> becomes invalid, such as when the clock starts or stops. You can register for this event with directly using a <xref:System.Windows.Media.Animation.Clock>, or you can register using a <xref:System.Windows.Media.Animation.Timeline>.
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In the following example, a <xref:System.Windows.Media.Animation.Storyboard> and two <xref:System.Windows.Media.Animation.DoubleAnimation> objects are used to animate the width of two rectangles. The <xref:System.Windows.Media.Animation.Timeline.CurrentStateInvalidated> event is used to listen for clock state changes.
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## Example
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[!code-xaml[timingbehaviors_snip#_graphicsmm_StateExampleMarkupWholePage](~/samples/snippets/csharp/VS_Snippets_Wpf/timingbehaviors_snip/CSharp/StateExample.xaml#_graphicsmm_stateexamplemarkupwholepage)]
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[!code-csharp[timingbehaviors_snip#_graphicsmm_StateEventHandlers](~/samples/snippets/csharp/VS_Snippets_Wpf/timingbehaviors_snip/CSharp/StateExample.xaml.cs#_graphicsmm_stateeventhandlers)]
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[!code-vb[timingbehaviors_snip#_graphicsmm_StateEventHandlers](~/samples/snippets/visualbasic/VS_Snippets_Wpf/timingbehaviors_snip/visualbasic/stateexample.xaml.vb#_graphicsmm_stateeventhandlers)]
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The following illustration shows the different states the animations enter as the parent timeline (*Storyboard*) progresses.
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The following table shows the times at which *Animation1*'s <xref:System.Windows.Media.Animation.Timeline.CurrentStateInvalidated> event fires:
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| Time (Seconds) | State |
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|----------------|-------|
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|1|Active|
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|10|Active|
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|19|Stopped|
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|21|Active|
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|30|Active|
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|39|Stopped|
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The following table shows the times at which *Animation2*'s <xref:System.Windows.Media.Animation.Timeline.CurrentStateInvalidated> event fires:
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| Time (Seconds) | State |
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|----------------|-------|
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|1|Active|
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|9|Filling|
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|11|Active|
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|19|Stopped|
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|21|Active|
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|29|Filling|
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|31|Active|
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|39|Stopped|
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Notice that *Animation1*'s <xref:System.Windows.Media.Animation.Timeline.CurrentStateInvalidated> event fires at 10 seconds, even though its state remains <xref:System.Windows.Media.Animation.ClockState.Active>. That's because its state changed at 10 seconds, but it changed from <xref:System.Windows.Media.Animation.ClockState.Active> to <xref:System.Windows.Media.Animation.ClockState.Filling> and then back to <xref:System.Windows.Media.Animation.ClockState.Active> in the same tick.
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