There are two types of errors that occur in Silverlight applications. Synchronous method calls will throw an error while the method is being called, but asynchronous errors can be thrown at anytime. Synchronous errors are normally handled by placing a try/catch block around the method call and asynchronous by attaching an event handler to the respective error event. A global level OnError event handler is called for both cases when an error is not handled by either a try/catch block or error event handler.
Silverlight will display a standard alert message box by default with some information about the error if a custom OnError event handler is not specified. You should try to
handle errors at the most granular level possible for the best user experience. You can also specify a custom
OnError event handler for unhandled errors when the Silverlight
plug-in is embedded.
Downloader object has a
DownloadFailed event which is raised when the requested content fails to load. You can check the
StatusText properties on the
Downloader object for additional information.
ImageBrush objects have an
ImageFailed event which is raised when the requested image fails to load or is in an incorrect format.
MediaElement object has a
MediaFailed event which is raised when the requested content fails to load, is in an incorrect format, or an unknown playback error occurs.
Related information on the web is listed below.