WPF 数据绑定和验证规则最佳实践

我有一个非常简单的 WPF 应用程序，其中我使用数据绑定来允许编辑一些自定义 CLR 对象。我现在想把一些输入验证时，用户单击保存。然而，我读过的所有 WPF 书籍并没有真正地在这个问题上投入任何篇幅。我看到您可以创建自定义 ValidationRules，但是我想知道这是否对于我的需要来说是过分的。

所以我的问题是: 是否有一个很好的示例应用程序或文章演示了在 WPF 中验证用户输入的最佳实践？

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最佳答案

I think the new preferred way might be to use IDataErrorInfo

Read more here

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Also check this article. Supposedly Microsoft released their Enterprise Library (v4.0) from their patterns and practices where they cover the validation subject but god knows why they didn't included validation for WPF, so the blog post I'm directing you to, explains what the author did to adapt it. Hope this helps!

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personaly, i'm using exceptions to handle validation. it requires following steps:

  1. in your data binding expression, you need to add "ValidatesOnException=True"
  2. in you data object you are binding to, you need to add DependencyPropertyChanged handler where you check if new value fulfills your conditions - if not - you restore to the object old value (if you need to) and you throw exception.
  3. in your control template you use for displaying invalid value in the control, you can access Error collection and display exception message.

the trick here, is to bind only to objects which derive from DependencyObject. simple implementation of INotifyPropertyChanged wouldn't work - there is a bug in the framework, which prevents you from accessing error collection.

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You might be interested in the BookLibrary sample application of the WPF Application Framework (WAF). It shows how to use validation in WPF and how to control the Save button when validation errors exists.

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From MS's Patterns & Practices documentation:

Data Validation and Error Reporting

Your view model or model will often be required to perform data validation and to signal any data validation errors to the view so that the user can act to correct them.

Silverlight and WPF provide support for managing data validation errors that occur when changing individual properties that are bound to controls in the view. For single properties that are data-bound to a control, the view model or model can signal a data validation error within the property setter by rejecting an incoming bad value and throwing an exception. If the ValidatesOnExceptions property on the data binding is true, the data binding engine in WPF and Silverlight will handle the exception and display a visual cue to the user that there is a data validation error.

However, throwing exceptions with properties in this way should be avoided where possible. An alternative approach is to implement the IDataErrorInfo or INotifyDataErrorInfo interfaces on your view model or model classes. These interfaces allow your view model or model to perform data validation for one or more property values and to return an error message to the view so that the user can be notified of the error.

The documentation goes on to explain how to implement IDataErrorInfo and INotifyDataErrorInfo.

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If your business class is directly used by your UI is preferrable to use IDataErrorInfo because it put logic closer to their owner.

If your business class is a stub class created by a reference to an WCF/XmlWeb service then you can not/must not use IDataErrorInfo nor throw Exception for use with ExceptionValidationRule. Instead you can:

  • Use custom ValidationRule.
  • Define a partial class in your WPF UI project and implements IDataErrorInfo.

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