Validation.Error Attached Event
[This documentation is for preview only, and is subject to change in later releases. Blank topics are included as placeholders.]
Occurs when the bound element runs into a validation error, but only for bindings with the NotifyOnValidationError value set to true.
Assembly: PresentationFramework (in PresentationFramework.dll)
XMLNS for XAML: http://schemas.microsoft.com/winfx/2006/xaml/presentation, http://schemas.microsoft.com/netfx/2007/xaml/presentation
The WPF data binding model enables you to associate ValidationRules with your Binding object. Validation occurs during binding target-to-binding source value transfer before the converter is called. The following describes the validation process:
When a value is being transferred from the target property to the source property, the data binding engine first removes any ValidationError that may have been added to the Validation.Errors attached property of the bound element. It then checks if there are any custom ValidationRules defined for that Binding, in which case it calls the Validate method on each of the ValidationRules until one of them runs into an error or until all of them pass.
Once there is a custom rule that does not pass, the binding engine creates a ValidationError object and adds it to the Validation.Errors collection of the bound element. When Validation.Errors is not empty, the Validation.HasError attached property of the element is set to true. Also, if the NotifyOnValidationError property of the Binding is set to true, then the binding engine raises the attached event on the element.
If all of the rules pass, the binding engine then calls the converter, if one exists.
If the converter passes, the binding engine calls the setter of the source property.
If the binding has an ExceptionValidationRule associated with it and an exception is thrown during step 4, the binding engine checks to see if there is a UpdateSourceExceptionFilter. You have the option to use the UpdateSourceExceptionFilter callback to provide a custom handler for handling exceptions. If an UpdateSourceExceptionFilter is not specified on the Binding, the binding engine creates a ValidationError with the exception and adds it to the Validation.Errors collection of the bound element.
For more information, see "Data Validation" in Data Binding Overview.
Windows 8 Consumer Preview, Windows Server 8 Beta, Windows 7, Windows Server 2008 SP2, Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.