public Geometry Project( 
   Geometry geometry,
   SpatialReference outputSpatialReference
)

Coordinate2D coordinate = new Coordinate2D(10, 30);
double angle = SpatialReferences.WGS84.GetConvergenceAngle(coordinate);
// angle = 0

SpatialReference srUTM30N = SpatialReferenceBuilder.CreateSpatialReference(32630);
coordinate.X = 500000;
coordinate.Y = 550000;
angle = srUTM30N.GetConvergenceAngle(coordinate);
// angle = 0

MapPoint pointWGS84 = MapPointBuilderEx.CreateMapPoint(10, 50, SpatialReferences.WGS84);
MapPoint pointUTM30N = GeometryEngine.Instance.Project(
  pointWGS84, srUTM30N) as MapPoint;

coordinate = (Coordinate2D)pointUTM30N;
// get convergence angle and convert to degrees
angle = srUTM30N.GetConvergenceAngle(coordinate) * 180 / Math.PI;
// angle = 10.03

//Create a point
var pt = MapPointBuilderEx.CreateMapPoint(x, y, 
               SpatialReferenceBuilder.CreateSpatialReference(4326));
//Buffer it - for purpose of zoom
var poly = GeometryEngine.Instance.Buffer(pt, buffer_size);

//do we need to project the buffer polygon?
if (!MapView.Active.Map.SpatialReference.IsEqual(poly.SpatialReference))
{
  //project the polygon
  poly = GeometryEngine.Instance.Project(poly, MapView.Active.Map.SpatialReference);
}

// Must run on MCT.
QueuedTask.Run(() =>
{
  //Zoom - add in a delay for animation effect
  MapView.Active.ZoomTo(poly, new TimeSpan(0, 0, 0, 3));
});

MapPoint pt = MapPointBuilderEx.CreateMapPoint(1.0, 3.0, SpatialReferences.WGS84);
Geometry result = GeometryEngine.Instance.Project(pt, SpatialReferences.WebMercator);
MapPoint projectedPt = result as MapPoint;

// create the polygon
List<MapPoint> pts = new List<MapPoint>();
pts.Add(MapPointBuilderEx.CreateMapPoint(1.0, 1.0, SpatialReferences.WGS84));
pts.Add(MapPointBuilderEx.CreateMapPoint(1.0, 2.0, SpatialReferences.WGS84));
pts.Add(MapPointBuilderEx.CreateMapPoint(2.0, 2.0, SpatialReferences.WGS84));
pts.Add(MapPointBuilderEx.CreateMapPoint(2.0, 1.0, SpatialReferences.WGS84));

Polygon polygon = PolygonBuilderEx.CreatePolygon(pts);
// ensure it is simple
bool isSimple = GeometryEngine.Instance.IsSimpleAsFeature(polygon);

// create the spatial reference to project to
SpatialReference northPole = SpatialReferenceBuilder.CreateSpatialReference(102018);   // north pole stereographic 

// project
Geometry geometry = GeometryEngine.Instance.Project(polygon, northPole);

//var featSceneLayer = ...;
//var sname = featSceneLayer.Name;
await QueuedTask.Run(() =>
{
  if (!featSceneLayer.HasAssociatedFeatureService)
    return;//no search or select

  //Select all features within the current map view
  var sz = MapView.Active.GetViewSize();
  var map_pt1 = MapView.Active.ClientToMap(new System.Windows.Point(0, sz.Height));
  var map_pt2 = MapView.Active.ClientToMap(new System.Windows.Point(sz.Width, 0));

  //Convert to an envelope
  var temp_env = EnvelopeBuilderEx.CreateEnvelope(map_pt1, map_pt2, MapView.Active.Map.SpatialReference);

  //Project if needed to the layer spatial ref
  SpatialReference sr = null;
  using (var fc = featSceneLayer.GetFeatureClass())
  using (var fdef = fc.GetDefinition())
    sr = fdef.GetSpatialReference();

  var env = GeometryEngine.Instance.Project(temp_env, sr) as Envelope;

  //Set up a query filter
  var sf = new SpatialQueryFilter()
  {
    FilterGeometry = env,
    SpatialRelationship = SpatialRelationship.Intersects,
    SubFields = "*"
  };

  //Select against the feature service
  var select = featSceneLayer.Select(sf);
  if (select.GetCount() > 0)
  {
    //enumerate over the selected features
    using (var rc = select.Search())
    {
      while (rc.MoveNext())
      {
        using (var feature = rc.Current as Feature)
        {
          var oid = feature.GetObjectID();
          //etc.
        }
      }
    }
  }

  MapView.Active.Map.ClearSelection();

});