Hi Dominique, thanks for the reply. I have set up the rotation expression as described for my DictionaryRenderer, and I then initialise the Graphic like this:
Dictionary<string, object> attributes = new Dictionary<string, object>();
attributes["ANGLE"] = boat.angle;
attributes["Style"] = "BoatImage";
Graphic graphic = new Graphic(boat.Location, attributes);
graphicsOverlay.Graphics.Add(graphic);
This correctly sets the rotation, but I don't see how to change the rotation after this. Modifying the attribute dictionary does not seem to have any effect. Am I misunderstanding how the attributes work?