There are 3 possible solutions which a user can go:
1) Use of pop-up window, which is called by an Event in Silverlight app and ASP.NET report viewer is being used as it is in the pop-up window. The Report customization is part of your report development.
The major issue here is pop-up blockers which by default comes with major browser and hence your pop-up would be blocked mostly causing a bad user experience. Good part is the solution works and presents you with the report.
2) Use of iframe on the same page where Silverlight app is also hosted. The iframe is hidden initially and based on the Silverlight Event this iFrame is made visible and hence we see the report inside an iframe.
Good part is it gives a good user experience and the report viewer looks continous and part of application.
Reference Link : http://sushantp.wordpress.com/2009/11/25/silverlight-reporting-support-for-ssrs-reports-problem-and-possible-solutions/http://sushantp.wordpress.com/2009/11/25/silverlight-reporting-support-for-ssrs-reports-problem-and-possible-solutions/