topic Re: Clusterer Graphics Layer using XY Event Source in ArcGIS API for Silverlight Questions

Clusterer Graphics Layer using XY Event Source

SimeonTelfer — Wed, 04 Aug 2010 01:19:10 GMT

Up until last week, we had a Silverlight application which used an XY Event Source Layer to populate a Cluster Graphics Layer, it worked exactly as expected. However, as of late last week (with no changes to the code),the cluster layer will not display in the app.

The layer displays fine as points on the map, the spatial reference appears to be correct, and when debugging, we can see that the graphics layer is being populated with the data. It just does not display. If the data is loaded into an SDE spatial feature class and used in place of the event layer, the cluster layer works correctly. We want to use an XY event though, as data is entered as Eastings and Northings through an external interface.

We are using Silverlight API 1.2, with Silverlight 3.0. The cluster graphics layer code we are using is from the ESRI Sample gallery.

Any ideas on why this has stopped working? Or has anyone else experienced this problem? Any help would be greatly appreciated as this app was due to go live in 2 weeks. I'm happy to give any further information or code if required. 🙂

Simeon

GIS Development and Support
Department for Water
Government of South Australia

Re: Clusterer Graphics Layer using XY Event Source

RexHansen — Fri, 13 Aug 2010 07:38:01 GMT

This behavior usually indicates something changed in the data source.

Just to clarify your statement "The layer displays fine as points on the map, the spatial reference appears to be correct, and when debugging, we can see that the graphics layer is being populated with the data. It just does not display." So just to confirm, does the XY event layer display successfully as points using marker symbols when clustering is not applied?

Have you tried using the default clusterer? Does it work?

Are you reprojecting the coordinates before display on the map?

For your custom clusterer, are you using the sample code referenced here? http://resources.esri.com/help/9.3/arcgisserver/apis/silverlight/samples/start.htm#CustomClusterer

Re: Clusterer Graphics Layer using XY Event Source

SimeonTelfer — Tue, 02 Nov 2010 23:37:18 GMT

I have worked out the issue, just in case anyone ever has this same problem.

Initially we discovered that if the X or Y field had a NULL value then the clusterer would not display any graphics at all, as opposed to the point event layer which would just not display the particular point with the NULL value. The event source we were using was actually a database view, so we filtered out any rows with a NULL value in the easting or northing.

This worked until one of the project officers (not a GIS person, obviously) entered the coordinates for a location backwards (i.e. easting and northing swapped). This caused the same problem of NO graphics being displayed at all. Coordinates are now validated on data entry.