System.ComponentModel.INotifyDataErrorInfois a Silverlight-only interface that defines members that data entity classescan implement to provide custom, asynchonous validation support. ImportantSilverlight user interface controls including the DataForm and DataGrid checkfor the implementation of this interface by data entities to which they arebound and provide excellent messaging in the user interface to help end userslearn about and correct validation errors.

Such Silverlight user interface controls do not depend uponexceptions being thrown in order to learn about validation problems. Instead,they subscribe to an ErrorChangedevent published by the entity as part of its INotifyDataErrorInfo compliance. That event is raised by the dataentity whenever it believes that a change to its state might be important tosome 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 exposeto the end user as its developer sees fit.

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