In this chapter, you've seen how you can design an adaptable plugin framework for the data tier and how interfaces can be used to construct a layer of abstraction on top of the database. You then learned how to set up the Oracle Lite and SQL Server CE databases on the mobile device and had a feel of the developer tools provided with these database installations.

You've also learned how you can use the various ADO.NET providers to connect to these databases, and run SQL statements to retrieve and update data to and from these databases. In building the two database plugins, you've learned how you can use ADO.NET datasets, command objects, and transactions to communicate effectively with the underlying databases.

Building a formidable data tier goes a long way in providing a robust foundation on top of which you can build your logic and presentation tier. In the next chapter, we will look at how we can make further use of the data tier we have built from the logic tier.