I have a VB6 app which calls a .NET assembly, which references settings from the app.config file. By default, .NET looks for a config file named after the VB6 app. How can I redirect it to use a different config file name? This needs to become the default config file so that e.g. WCF settings are read from it.
You can't change it. Each AppDomain instance has a fixed app.config that is set via an AppDomainSetup instance when a new app domain is created. Although you can get the setup information via AppDomain.SetupInformation it has effectively become readonly at this point.
Given this, one option may be to create a new app domain from within your Main function and configure the domain to use the app.config you require.