// Change an existing directshape to a new geometry without recreating it
public void ChangeDS(){
			
			UIDocument uidoc = this.ActiveUIDocument;
			Document doc = uidoc.Document;
			
			List<Curve> profile = new List<Curve>();
		
		    // first create sphere with 2' radius
		    XYZ center = XYZ.Zero;
		    double radius = 5.0;    
		    XYZ profile00 = center;
		    XYZ profilePlus = center + new XYZ(0, radius, 0);
		    XYZ profileMinus = center - new XYZ(0, radius, 0);
		
		    profile.Add(Autodesk.Revit.DB.Line.CreateBound(profilePlus, profileMinus));
		    profile.Add(Arc.Create(profileMinus, profilePlus, center + new XYZ(radius, 0, 0)));
		
		    CurveLoop curveLoop = CurveLoop.Create(profile);
		    SolidOptions options = new SolidOptions(ElementId.InvalidElementId, ElementId.InvalidElementId);
		
		    
		    options.MaterialId = new ElementId(39301);
		    
		    
		    Frame frame = new Frame(center, XYZ.BasisX, -XYZ.BasisZ, XYZ.BasisY);
		    Solid sphere = GeometryCreationUtilities.CreateRevolvedGeometry(frame, new CurveLoop[] { curveLoop }, 0, 2 * Math.PI, options);
		    
			IList<Reference> s = uidoc.Selection.PickObjects(ObjectType.Element,"select");
			
			DirectShape ds = doc.GetElement(s.First()) as DirectShape;
			
						using (Transaction t = new Transaction(doc, "isolate view")){
				t.Start();
				
			ds.SetShape(new GeometryObject[] { sphere });
			t.Commit();
			}
		}