dll reference for ASP.NET website project not working

I have created a console application in C# to access databases.
Later, I changed the output type to Class Library.
the framework is set to .NET framework 4.

I have crated a ASP.NET Empty Website project.
I want to add my dll reference to this.

Things I've tried:
1. Right click project and add reference --> browse to C# project location --> add .dll file from bin/debug folder

--The above does not work

2. I've tried to add the .dll file from original location directly in root project folder of ASP.NET website, and then add a reference to this copy of the .dll file.
-- What this does is creates a copy under Bin folder
--This also doesn't work.

When I say it doesn't work, I'm trying to add a Using reference in the ASP.NET website. The default.aspx.cs page, does not have any namespace (by default).
Also, I've checked that .NET framework for ASP.NET website is set to .NET 4 (not .NET 4 client).

Can anyone please suggest what might be going wrong? your help and ideas will be greatly appreciated.

P.S. The .pdb file, which gets added when you add the .dll file in Bin folder, has a RedDot on the icon. Suggesting it might be some sort of an error. When i complied the original .cs file, of the class library, no errors were found. Also, no main class exists in original C# project, since it is a class library.

Tags: ASP.NET