silverlight forms authentication heartbeat

I have a silverlight application protected by forms authentication. I want the开发者_C百科 forms authentication to stay alive as long as the silverlight application is up.

I created a heartbeat web.service that silverlight calls. In the web motheod I set a session variable.

However I am still having trouble with the forms authentication kicking in.

Any idea what might be causing it and what the best proactice for keeping forms authentication alive is?

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I believe you can turn on sliding expiration.

http://msdn.microsoft.com/en-us/library/system.web.security.formsauthentication.slidingexpiration.aspx