/// <summary>
/// Returns the AnnotationService enabled for the viewer. If no service is
/// enabled for the viewer, returns null.
/// </summary>
/// <param name="viewer">viewer to check for an enabled AnnotationService</param>
/// <returns>the AnnotationService instance for this viewer, null if a service
/// is not enabled for this viewer</returns>
/// <exception cref="ArgumentNullException">viewer is null</exception>
public static AnnotationService GetService(FlowDocumentScrollViewer viewer)
{
if (viewer == null)
throw new ArgumentNullException("viewer");
return viewer.GetValue(AnnotationService.ServiceProperty) as AnnotationService;
}
