I have an application that I want to be able to configure the connection string for my LINQ to SQL. I've tried so many different ways but cannot seem to get it working. I want to do this dynamically in the code when the app is run, the reason for this is that the user can change the connection settings.

If I delete the connectionString out of app.config the application still works OK (communicating) which makes me wonder where I should be changing the connection string?