asp.net web application: assembly generation failed referenced assembly does not have a strong name

in my asp.net web application I got this problem when added a new class library into my solution and trying to build the solution:
"assembly generation failed referenced assembly does not have a strong name"

Apparently the solution is to go to the class Project properties: Solution Explorer > right click > properties, click on Signing tab, select "Sign the assembly", then browse the key shared among other projects within the same solution.