Do you know a manual that explain how to use those DB's... preferably with code samples.
Thanks Asaf
If you are using .NET Compact framework, there is the Sql Server Compact Edition. As for the manuals, you can always find something related to this on MSDN. (I am not sure what you mean by native database.)
There may be examples of Perst for Windows Phone 7 or other C# ports of SQL-like Database implementations in this is for Windows Phone 7 - access to SQL CE on the phone is currently unavailable to developers at this time. Look for some examples of these being used and you'll find most of the information on these. SQL CE for Windows Phone 7 may be available at some point in the future for developers, however nothing has been announced or confirmed regarding this.
Currently, Windos Phone 7 does not come with native database support for developers. You have 3 options for storing data: 1. Use the isolated storage of the phone 2. Store your data using a cloud service 3. user a non-native db such as Perst.
If you have a small amount of data, then serialize it to xml or json file, and store it on the isolated storage of the phone.
If your data is large, you will need to use a cloud service or a database such as perst.
If by "native" you mean "already residing on the phone" then you don't have a whole lot of options. SQL Compact is already built in to the device - you just can't yet use it from 3rd party applications in the first platform release. There simply isn't a database engine already on the platform that is available to third-party developers.
Your only option for persistent storage out of the box is isolated storage. Microsoft does not ship any database engine usable by third parties that uses that, so your options are to either use a third party solution like Perst (which has been around for a while) or SQLite (I've started the port to my ORM) or to roll your own.