Silverlight session

Hello, session is a server side concept. Silverlight runs on the client, so it has no knowledge of the session. But you can pass some variable from the Silverlight application to the server via a web service. Then in the web service, you store it as a session variable. Later when you call another web service, you can check the session variable and return it to the client.
While WCF also has built-in session support, BasicHttpBinding doesn't support that. So you need to use ASP.NET session instead. To enable ASP.NET session on WCF, you need to turn on ASP.NET Compatibility. Do the following:
In web.config, under system.serviceModel tag, add this line:
<servicehostingenvironment aspnetcompatibilityenabled="true">
On your service class (not interface), add this attribute:
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
Now you can use ASP.NET session with the following syntax:
HttpContext.Current.Session["YourName"] = something;
object something = HttpContext.Current.Session["YourName"];
That being said, I think in your scenario, it's better to store your object on the client side using isolated storage or an application level variable.