Project cannot be started error

Project cannot be started error

I have a solution with three projects in it. One is the business layer
which has an output set to class library. The second is a UI layer which
is currently setup as a console application and the third is a unit test
project.
I have referenced the business layer application in my UI and set the
startup object to UI.Program but when I try to run the application I get
the following error:
A project with an output type of class Library cannot be started directly
In order to debug this project, add an executable project to this solution
which references the library project. Set the executable project as the
startup project.
I cant find the source of this error, and I've tried what others have done
to fix this problem with no luck. Any suggestions?