public void Scale( 
   SelectionSet features,
   MapPoint origin,
   double sx,
   double sy,
   double sz
)

var scaleFeatures = new EditOperation() { Name = "Scale Features" };

//Rotate works on a selected set of features

//var scaleSelection = MapView.Active.GetFeatures(polygon).Select(
//    k => new KeyValuePair<MapMember, List<long>>(k.Key as MapMember, k.Value));
//scaleFeatures.Scale(scaleSelection, origin, 2.0, 2.0, 0.0);

//Scale the selected features by 2.0 in the X and Y direction
scaleFeatures.Scale(MapView.Active.GetFeatures(polygon), origin, 2.0, 2.0, 0.0);

//Execute to execute the operation
//Must be called within QueuedTask.Run
if (!scaleFeatures.IsEmpty)
{
  var result = scaleFeatures.Execute(); //Execute and ExecuteAsync will return true if the operation was successful and false if not
}

//or use async flavor
//await scaleFeatures.ExecuteAsync();