How to centralize these business rules into a Business Logic Layer (BLL) that serves as an intermediary for data exchange between the presentation layer and the DAL.
In a real-world application, the BLL should be implemented as a separate Class Library project; however, for these tutorials we'll implement the BLL as a series of classes in our App_Code folder in order to simplify the project structure.
All Tutorials:
http://www.asp.net/learn/dataaccess/default.aspx?tabid=63
Tutorial 1: Creating a Data Access Layer
http://msdn.microsoft.com/asp.net/reference/data/default.aspx?pull=/library/en-us/dnaspnettut/html/aspnet_tutorial01_dataaccesslayer_vb.asp
Tutorial 2: Creating a Business Logic Layer
http://msdn.microsoft.com/asp.net/reference/data/default.aspx?pull=/library/en-us/dnaspnettut/html/aspnet_tutorial02_businesslogiclayer_vb.asp
Tutorial 3: Master Pages and Site Navigation
http://msdn.microsoft.com/asp.net/default.aspx?pull=/library/en-us/dnaspnettut/html/aspnet_tutorial03_masterpagesandsitenav_vb.asp
Tutorial 4: Displaying Data With the ObjectDataSource
http://msdn.microsoft.com/asp.net/default.aspx?pull=/library/en-us/dnaspnettut/html/aspnet_tutorial04_datawithobjectdatasource_vb.asp
Tutorial 5: Declarative Parameters
http://msdn.microsoft.com/asp.net/default.aspx?pull=/library/en-us/dnaspnettut/html/aspnet_tutorial05_declarativeparameters_vb.asp
Tutorial 6: Programmatically Setting the ObjectDataSource's Parameter Values
http://msdn.microsoft.com/asp.net/default.aspx?pull=/library/en-us/dnaspnettut/html/aspnet_tutorial06_programmaticallysetparamvalues_vb.asp
