I have an automated build process that sets up the application for a specified mode (e.g. Dev, uat, live). Depending on this mode I want to update Connection Strings to the rele
Yeah, you're doing it backwards. The IDE generates the .config file contents from the settings you define in the Settings designer. That doesn't work the other way around. If getting the connection string valid straight from the build is important then set the default in the Settings designer. Or don't store it in a setting.
There is a way to override the settings.settings :
Project.Properties.Settings.Default["ConnectionString"] = ConfigurationManager.ConnectionStrings["Project.Properties.Settings.ConnectionString"].ConnectionString;