Invalid spatial reference

Question

Im getting this error when I switched to a different map. This map works fine http://services.arcgisonline.com/ArcGIS/rest/services/ESRI_Imagery_World_2D/MapServer This map give me the error http://services.arcgisonline.com/ArcGIS/rest/services/NatGeo_World_Map/MapServer private void AddMarker(UnitUI unit) { var graphic = new Graphic() { Symbol = GetSymbol(unit) }; double lat = unit.Base.Latitude; double lng = unit.Base.Longitude; var point = new MapPoint(lng, lat); point.SpatialReference = MyMap.SpatialReference; graphic.Geometry = new WebMercator().FromGeographic(point); <--error here "Invalid spatial reference " GraphicsLayer.Graphics.Add(graphic); }

DominiqueBroux · Answer

MyMap.Extent = newExtent;

To get that working the newExtent must be in the same SpatialReference than the map.
So if your map is using WebMercator, your extent must be in WebMercator as well.

Try something like:
var point = new MapPoint(lat, lng, new SpatialReference(4326));
if (!point.SpatialReference.Equals(MyMap.Spatialreference))
   point = new WebMercator().FromGeographic(point); // assuming your map is either in web mercator or in geographical coordinates. Might be more complex if you need to take all others cases into account

Envelope newExtent = new Envelope(point.X - halfWidth, point.Y - halfHeight, point.X + halfWidth, point.Y + halfHeight);
MyMap.Extent = newExtent;

JenniferNery · Answer

The problem seems to be that your map is WKID=3857 and you want to zoom to an extent with WKID=4326. Since you already have the resolution, maybe you should call ZoomToResolution, there is an overload for including MapPoint http://help.arcgis.com/en/webapi/silverlight/apiref/ESRI.ArcGIS.Client~ESRI.ArcGIS.Client.Map~ZoomToResolution%28Double,MapPoint%29.html

TylerRothermund · Answer

If your map is already using Geographical coordinates, you don't need any projection (assuming that your lng and lat are always geographical coordinates whatever the map SR)

So, this should work:
var point = new MapPoint(lng, lat, new SpatialReference(4326)); 
if (MyMap.SpatialReference.WKID == 4326) // Geographic coordinates
{
  graphic.Geometry = point;
}
else
{
  graphic.Geometry = new WebMercator().FromGeographic(point); 
}

That being said, from 2.3, the graphics layer is able to autoproject the geometry.
So this sould work as well:graphic.Geometry = new MapPoint(lng, lat, new SpatialReference(4326));

So that seemed to fix the original problem but now my ZoomTo isn't working private void ZoomTo(double lat, double lng, int level)
        {
            var newResolution = GetResolution(level);
            double halfWidth = newResolution * MyMap.ActualWidth / 2;
            double halfHeight = newResolution * MyMap.ActualHeight / 2;
            var point = new MapPoint(lat, lng, new SpatialReference(4326));

Envelope newExtent = new Envelope(point.X - halfWidth, point.Y - halfHeight, point.X + halfWidth, point.Y + halfHeight);
            MyMap.Extent = newExtent;
        }