BitmapImage.ImageOpened Event
Silverlight
Occurs when the image source is downloaded and decoded with no failure. You can use this event to determine the size of an image before rendering it.
Namespace: System.Windows.Media.Imaging
Assembly: System.Windows (in System.Windows.dll)
If the image-decode fails for any reason, this event does not fire. Once this event fires, the PixelHeight and PixelWidth properties are guaranteed to be valid.
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.