Location position = wall.Location as Location;
if (null != position) {
XYZ axisStart = new XYZ(sp.X, sp.Y, 0);
XYZ axisEnd = new XYZ(sp.X, sp.Y, 1);
Line axis = Line.CreateBound(axisStart, axisEnd);
position.Rotate(axis, a/2);
}
position = wall.Location as Location;
if (null != position) {
XYZ axisStart = new XYZ(ep.X, ep.Y, 0);
XYZ axisEnd = new XYZ(ep.X, ep.Y, 1);
Line axis = Line.CreateBound(axisEnd, axisStart);
position.Rotate(axis, -a / 2);
}