title: where to write the connection string ? in app.config or in web.config?
body: <p>I am developing MVC application.
  I have two projects in my application. 
  one is MVC application contains, Controller and Views and the second one is DataLayer project. </p>
  
  <p>I am confused about the where to write the connection string, because while publishing the application it takes the web.config file and I get the data from DataLayer project so should I add connection string in the app.config/Web.config of Data layer project  ? </p>
  
  <p>Also, would like to know what is the purpose and difference between app.config and web.config   ? </p>