>When doing 3-tier code:
>presentation/business/data layers
>
>Should one use the codebehind as a separate tier? Or not use it at all and just have class libraries for the 3 layers?
>
>I mean page controlling code should be separate from the html code, but do we want code in codebehind (one page for each html page) or in a middle-tier?
>
>Thanks for any ideas.


Interesting point since all the code behind is being compiled as a single DLL in the \Bin directory.

This is what I do:
presentation tier: HTML + code behind
business tier: code behind + Business rules in DLL
data tier: SQL Server

As you can see, I think there's a grey area in what code behind must do.