A dll assembly in .NET CAN NOT have a config file that it can access just as an exe assembly can through ConfigurationSettings.AppSettings or .GetConfig - However, it can access the application's config file through the ConfigurationSettings class.

If you're looking for a way to have the dll assembly to access its own config file take a look at what Enterprise library has with their configuration block. The configuration file does not follow the convention of the .NET Configuration files.

There are some videos on my website that I recorded - Hisham Baz is person presenting and is one of the architects of the Enterprise Library: http://www.dandyvibe.com