Local Database with Silverlight

What would be a good local database for a Silverlight application? The database's main purpose is for local data caching and synchronization services. I do not believe that SQL anywhere or SQLite will work since they use unmanaged code which will not run under the silverlight sandbox

Why don't use a new feature in SL 2 called "Isolated Storage"? It is fully support in local database (like Google Gear) but of course It is not a database. You can use XML file format to keep it.

pros; User just need to install SL runtime.
cons; It's not exactly a database

Find two references:

Moth said in his blog about it http://www.danielmoth.com/Blog/2008/04/isolatedstorage-in-siverlight-2-beta-1.html Dino made very good summary at http://www.ddj.com/windows/208300036?pgno=2