public Geometry GetGraphicOutline()

{

  // Note: QueuedTask is required to access the AnnotationFeature
  {
    //get the first annotation feature...
    //...assuming at least one feature gets selected
    using var fc = annotationLayer.GetFeatureClass();
    using var rc = fc.Search();
    rc.MoveNext();
    using var af = rc.Current as AnnotationFeature;
    var outline_geom = af.GetGraphicOutline();
    //TODO - use the outline...

    //Note: 
    //var graphic = annoFeature.GetGraphic(); 
    //gets the CIMTextGraphic...
  }
}