The Silverlight client has some self imposed URL access restrictions
, which may catch you out from time to time.
The most common, cross domain calls, are easy to spot as when something doesn't work you will no doubt fire up fiddler
and see the request for the cross domain policy file. This will remind you what you need to do ;)
I haven't come across the need to implement cross scheme calls yet, but cross-zone calls have caught me out, as until you encounter it you might not even think it would be an issue.
There is no error generated for a cross-zone call being blocked, there is also no traffic generated from Silverlight (so nothing in Fiddler), the call is blocked before any connection is attempted. So to the developer, your app loads and any calls to the services hosted 'cross zone' will not work, with no apparent reason.
If this happens to you, you need to check your Internet Explorer settings (even for Firefox hosted Silverlight) to make sure that the client and the server are in the same zone. If they are not you can change your client/server URLs, where they are hosted or change the zone settings in IE (your system administrator may need to push a policy out to intranet users if you choose this option)