System.ComponentModel.INotifyDataErrorInfo is a Silverlight-only interface that defines members that data entity classes can implement to provide custom, asynchonous validation support. Important Silverlight user interface controls including the DataForm and DataGrid check for the implementation of this interface by data entities to which they are bound and provide excellent messaging in the user interface to help end users learn about and correct validation errors.

Such Silverlight user interface controls do not depend upon exceptions being thrown in order to learn about validation problems. Instead, they subscribe to an ErrorChanged event published by the entity as part of its INotifyDataErrorInfo compliance. That event is raised by the data entity whenever it believes that a change to its state might be important to some control in the user interface. The UI control, learning of such a change, can then query the data entity via its INotifyDataErrorInfo.GetErrors() method to obtain a current set of validation errors, which it may then expose to the end user as its developer sees fit.

Because of the support for INotifyDataErrorInfo by Silverlight UI controls, most developers working in Silverlight will want to set the system default for VerifierOptions.ErrorNotificationMode to Notify rather than any setting that results in exceptions being thrown for validation errors.