Setting this property provides an alternative to use the DataErrorValidationRule element, explicitly. The DataErrorValidationRule is a built-in validation rule that checks for errors that are raised by the "IDataErrorInfo" implementation of the source object. If an error is raised, the binding engine creates a ValidationError with the error and adds it to the "Validation.Errors" collection of the bound element. The lack of an error clears this validation feedback, unless another rule raises a validation issue.
This example shows how to implement validation logic on a custom object and then bind to it.
You can provide validation logic on the business layer if your source object implements IDataErrorInfo, as in the following example. In the following example, the "text" property of the textbox binds to the "Age" property of the Person object which has been made available for binding through a resource declaration that is given in the x:Keydata. The "DataErrorValidationRule" checks for the validation errors raised by the IDataErrorInfo implementation.