App.Config in two places

Hi, I created an app.config with a connection string in my class library and I tested my functions. All it's working perfectly.
When I put this dll in my application in other solution, I have put the connection string again.
How can I make only app.config of my class library to be the main app.config? I don't want to put other connection string because they are the same.
Thanks.
Thiago (from Brazil)