Sql – Are Linq to sql objects serializable for session state

Without going into whether this is a good or bad idea:

Is it possible to store a LINQ-to-SQL domain object in the ASP.NET Session, when the session is out-of-process?

[EDIT]
I'm currently getting the following error and asked this question because I suspect the LINQ-to-SQL objects:

Unable to serialize the session state. In 'StateServer' and 'SQLServer' mode, ASP.NET will serialize the session state objects, and as a result non-serializable objects or MarshalByRef objects are not permitted. The same restriction applies if similar serialization is done by the custom session state store in 'Custom' mode.
[/EDIT]

e.g.

Session["Zoo"] = new Zoo() { 
                         new Lion(),
                         new Tiger(), 
                         new Elephant()
                  }

where:

• Zoo, Lion, Tiger, Elephant all come out of a ZooDataContext

and the web.config file contains

<sessionState
       mode="StateServer"
       stateConnectionString="tcpip=127.0.0.1:42424"
       stateNetworkTimeout="10"
       sqlConnectionString="SqlStateConnectionString"
       sqlCommandTimeout="30"
       timeout="20"
       regenerateExpiredSessionId="true"/>