set the connection string in a LINQ dbml file dynamically (based on app.config)

Question

In a C# 2010  console application I am having the same problem that is listed in the following url:
http://ddkonline.blogspot.com/2008/02/set-connection-string-in-linq-dbml-file.html.

However I am having the problem wih an app.config file.

My question is in the article, that refers to the "InvestmentManagementConnectionString", how do I connection this to the app.config file?

Can you show me me how the app.config file would be setup to reference the "InvestmentManagementConnectionString"?