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34 lines
2.0 KiB
Markdown
34 lines
2.0 KiB
Markdown
---
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title: "How to: Implement Validation Logic on Custom Objects"
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ms.date: "08/02/2018"
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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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- "checking for validation errors [WPF]"
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- "validation errors [WPF], checking for"
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- "implementing validation logic on custom objects [WPF]"
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- "custom objects [WPF], implementing validation logic on"
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ms.assetid: 751fda9b-44f9-4d63-b4f2-1df07ac41e0f
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---
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# How to: Implement Validation Logic on Custom Objects
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This example shows how to implement validation logic on a custom object and then bind to it.
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## Example
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You can provide validation logic on the business layer if your source object implements <xref:System.ComponentModel.IDataErrorInfo>, as in the following example, which defines a `Person` object that implements <xref:System.ComponentModel.IDataErrorInfo>:
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[!code-csharp[BusinessLayerValidation#IDataErrorInfo](~/samples/snippets/csharp/VS_Snippets_Wpf/BusinessLayerValidation/CSharp/Data.cs#idataerrorinfo)]
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[!code-vb[BusinessLayerValidation#IDataErrorInfo](~/samples/snippets/visualbasic/VS_Snippets_Wpf/BusinessLayerValidation/VisualBasic/Data.vb#idataerrorinfo)]
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In the following example, the text property of the text box binds to the `Person.Age` property, which has been made available for binding through a resource declaration that is given the `x:Key` `data`. The <xref:System.Windows.Controls.DataErrorValidationRule> checks for the validation errors raised by the <xref:System.ComponentModel.IDataErrorInfo> implementation.
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[!code-xaml[BusinessLayerValidation#BoundTextBox](~/samples/snippets/csharp/VS_Snippets_Wpf/BusinessLayerValidation/CSharp/Window1.xaml?highlight=8,11-19,25-42)]
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Alternatively, instead of using the <xref:System.Windows.Controls.DataErrorValidationRule>, you can set the <xref:System.Windows.Data.Binding.ValidatesOnDataErrors%2A> property to `true`.
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## See also
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- <xref:System.Windows.Controls.ExceptionValidationRule>
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- [Implement Binding Validation](how-to-implement-binding-validation.md)
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- [How-to Topics](data-binding-how-to-topics.md)
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