I think you should means the "visual center", that's not a GIS concept and we don't have an API for it, this code can get a similar point which is in the edge of shape, you can adjust its X or Y to make it contained by the shape.
PolygonShape p = new PolygonShape();
PointShape centerPoint = p.GetCenterPoint();
centerPoint = p.GetClosestPointTo(centerPoint, GeographyUnit.Meter);
If the result is not enough for your target, you can also refer this topic to write your custom logic about this point.
Wish that's helpful.