here's a 'workaround' for dynamic display:
//create your EllipticArcClass as you would according to the ESRI documentation then get
//the points that make up the ellipse and create a polygon based on it - not efficient but it works
List<PointClass> points = new System.Collections.Generic.List<PointClass>();
//the level of fidelity should be adjusted
for(double d = 0.1; d < ellipticalArc.Length; d += 0.1)
{
PointClass p = new PointClass();
ellipticalArc.QueryPoint(esriSegmentExtension.esriNoExtension, d, false, p);
points.Add(p);
}
polygon = new PolygonClass();
foreach (PointClass p in points)
polygon.AddPoint(p);
ITopologicalOperator topo = polygon as ITopologicalOperator;
topo.Simplify();
//added polygon using graphicTracker and simplefillsymbol