database object

Question

I want to implement 3 tier architecture for library web application. In order to do that I want help regarding constructing database objects in C#. 

I want to implement class in C# that can hold any kind of data, I have seen previously people use <T> as some object.

Can any one please give me some exaple of this kind of programming.
I will really appreciate any kind of help, any article or any example.. Please help me out...

Thank you ,