FAQs

Problem: Cannot load data from my server

If accessing ArcGIS Server services, make sure that the ArcGIS Services Directory is setup and functioning. Navigate to http://<host>/arcgis/rest/services in a browser. You should see the Services Directory main page.
Make sure the REST endpoint for the service is available. Copy and paste the Url defined in your Silverlight\WPF application into a browser. For example: http://<host>/arcgis/rest/services/USA/MapServer
If your Silverlight application is not hosted on the same server or domain as the data (services) you are accessing, you need a clientaccesspolicy.xml file on the remote server. See the next FAQ for more information.
Use the InitializationFailure event on the layer to determine if an error is occuring and interrogate the error message.
View the HTTP request and response using a standard tool for interrogating HTTP communication. For example Fiddler, Silverlight Spy, FireBug (FireFox add-on), etcetra to determine if a failure has occured.

Problem: Cannot load data from an external data source outside your Silverlight application's domain

To access data from a remote server (a different server from the one where your Silverlight application is hosted), the remote server needs to have a clientaccesspolicy.xml file in the web servers root directory. For security reasons, a Web browser is not allowed to access data that resides outside the exact Web domain where the Silverlight XAP file originated. However, a Silverlight application can load data across domains if permission is granted from the server. This is accomplished by having a small clientaccesspolicy.xml file on the remote server that permits Silverlight to connect to services on that server. For additional information, read the topic Making a Service Available Across Domain Boundaries. For more information on the structure and function of a clientaccesspolicy.xml file, read the topic Network Security Access Restrictions in Silverlight 2.

As an example, you can also view the policy file used by ArcGIS Online: http://services.arcgisonline.com/clientaccesspolicy.xml
Problem: Tasks return a limited number of features

By default, queries against ArcGIS Server services are limited to returning 500 features and MapIt services are limited to 1000 features at a time. Both limits can be modified on the server, if you have access. If not, you will need to iterate through consecutive blocks of results on the client by using the field that contains a unique key (e.g. primary key) to track progress.
Problem: Accessing a Silverlight application on a Web server returns error code 2103 in the browser.

This error may indicate that a set of mime types needed to support Silverlight applications must be added to the Web server which will host your application. Add the following mime types:
```
.xaml  application/xaml+xml 
.xap   application/x-silverlight-app 
.xbap  application/x-ms-xbap              
```
If necessary, use Microsoft's Configuring IIS for Silverlight Applications document as a guide.
Problem: Cached or dynamic map images generated by an ArcGIS Server map service do not display transparent areas as transparent.

The Silverlight 2 platform does not support transparency in PNG 8-bit images. To define a transparent color in a map image generated by an ArcGIS Server map service (e.g. for the background) you need to generate a 24 or 32-bit PNG. By default, the ArcGIS Silverlight/WPF API will request a 24-bit PNG with a transparent background from ArcGIS Server dynamic map services. To render transparent areas correctly in cached map tiles, generate tiles in 24 or 32-bit PNG format.