To avoid too much formula, you can also use a CompositeTransform:
public static class GeometryExtension
{
public static Polyline Rotate(this Polyline polyline, double rotation, MapPoint fixPoint)
{
var transform = new CompositeTransform {Rotation = rotation, CenterX = fixPoint.X, CenterY = fixPoint.Y};
var output = new Polyline();
foreach(var path in polyline.Paths)
{
var pc = new ESRI.ArcGIS.Client.Geometry.PointCollection();
foreach (var mapPoint in path)
pc.Add(mapPoint.Transform(transform));
output.Paths.Add(pc);
}
return output;
}
private static MapPoint Transform(this MapPoint mapPoint, Transform transform)
{
var point = transform.Transform(new System.Windows.Point(mapPoint.X, mapPoint.Y));
return new MapPoint(point.X, point.Y);
}
}
Then you can rotate a polyline by code like : var result = myPolyline.Rotate(angle, fixPoint);
