I have created a small solution for practice.
Soulution Name : Sample
Class Library : Sample.ClassDB (Data Layer)
Class Library : Sample.ClassLib (Business Layer)
UI : Sample.UI (Which has webpart code)
In Sample.ClassLib project have refrence of "Sample.ClassDB" and "Sample.UI" has reference of "Sample.ClassLib".
In sharepoint package i added both assembly to make the safe control entry by clicking on Advance tab in package designer.
When tried to deploy the solution i received the below error.
The type or namespace name 'ClassDB' does not exist in the namespace 'Sample' (are you missing an assembly reference?)
Please suggest.
Akhilesh Rao