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34 lines
2.9 KiB
Markdown
34 lines
2.9 KiB
Markdown
---
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title: "How to: Implement a Dependency Property"
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description: Define a dependency property in Windows Presentation Foundation, by backing a common language runtime property with a DependencyProperty field.
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ms.date: "03/30/2017"
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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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- "dependency properties [WPF], backing properties with"
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- "properties [WPF], backing with dependency properties"
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ms.assetid: 855fd6d7-19ac-493c-bf5e-2f40b57cdc92
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---
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# How to: Implement a Dependency Property
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This example shows how to back a common language runtime (CLR) property with a <xref:System.Windows.DependencyProperty> field, thus defining a dependency property. When you define your own properties and want them to support many aspects of [!INCLUDE[TLA#tla_winclient](../../../includes/tlasharptla-winclient-md.md)] functionality, including styles, data binding, inheritance, animation, and default values, you should implement them as a dependency property.
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## Example
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The following example first registers a dependency property by calling the <xref:System.Windows.DependencyProperty.Register%2A> method. The name of the identifier field that you use to store the name and characteristics of the dependency property must be the <xref:System.Windows.DependencyProperty.Name%2A> you chose for the dependency property as part of the <xref:System.Windows.DependencyProperty.Register%2A> call, appended by the literal string `Property`. For instance, if you register a dependency property with a <xref:System.Windows.DependencyProperty.Name%2A> of `Location`, then the identifier field that you define for the dependency property must be named `LocationProperty`.
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In this example, the name of the dependency property and its CLR accessor is `State`; the identifier field is `StateProperty`; the type of the property is <xref:System.Boolean>; and the type that registers the dependency property is `MyStateControl`.
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If you fail to follow this naming pattern, designers might not report your property correctly, and certain aspects of property system style application might not behave as expected.
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You can also specify default metadata for a dependency property. This example registers the default value of the `State` dependency property to be `false`.
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[!code-csharp[PropertySystemEsoterics#MyStateControl](~/samples/snippets/csharp/VS_Snippets_Wpf/PropertySystemEsoterics/CSharp/SDKSampleLibrary/class1.cs#mystatecontrol)]
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[!code-vb[PropertySystemEsoterics#MyStateControl](~/samples/snippets/visualbasic/VS_Snippets_Wpf/PropertySystemEsoterics/visualbasic/sdksamplelibrary/class1.vb#mystatecontrol)]
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For more information about how and why to implement a dependency property, as opposed to just backing a CLR property with a private field, see [Dependency Properties Overview](dependency-properties-overview.md).
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## See also
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- [Dependency Properties Overview](dependency-properties-overview.md)
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- [How-to Topics](properties-how-to-topics.md)
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