First of all, add the new website to the Silverlight application (if your solution has an ASP.NET website) by right-clicking ProjectSolution> Add> New Website .
Now Rightclick on the ASP.NET website and click "Proportions." Now click the Silverlight Applications tab. Now click Add and select Use an existing project in the solution. You can now see the name of the Silverlight application. Now click Add again to add the Silverlight application to the ASP.NET website.
After that, set the ASP.NET website as the Startup Project and..TestPage.aspx as the start page.
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