Good example of DAL?

Hi,

I need a good example as to how to get started with creating a DAL. A link on another site would be fine too.
What I am looking for is a base class with appropriate functions for creating connections. A sample class that inherits this base class. And then all the classes that inherit this base should have transaction rollback capabilities.
I am familiar with running queries and stored procedures, just need a good reference for the object orientation of this process. Where can I find a good example of this?

Thanks 

using .NET 2.0, SQL 2005
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