Compared to the SDK sample, you have to take care of 2 points:1) the spatial reference of your service is probably not the same than the map spatial reference. So you have to initialize it by something like :
ESRI.ArcGIS.Client.Tasks.Query query = new ESRI.ArcGIS.Client.Tasks.Query()
{
Geometry = new ESRI.ArcGIS.Client.Geometry.Envelope(-180, 0, 0, 90) { SpatialReference = new ESRI.ArcGIS.Client.Geometry.SpatialReference(4326) },
OutSpatialReference = new ESRI.ArcGIS.Client.Geometry.SpatialReference(4326),
ReturnGeometry = true
};
query.OutFields.Add("*");
2) Your geometry is Point instead of Polygon so you have to initialize the symbol with a marker symbol instead of a fill symbol:
feature.Symbol = LayoutRoot.Resources["MarkerSymbol"] as Symbol;
That being said, the easiest way is to use a feature layer which is doing this work for you without any code(and which is using the symbology defined at server side).
<esri:FeatureLayer Mode="Snapshot" OutFields="*"
Url="http://irnrgis.tamu.edu/ArcGIS/rest/services/Test/Trims/MapServer/0" />