Cannot find my config file

Question

I need to read/write to a config file not related to any exe. I'm trying this:

        var appConfiguration = ConfigurationManager.OpenMappedExeConfiguration(new ExeConfigurationFileMap() { ExeConfigFilename = "SlamDunkSuper.config" }, ConfigurationUserLevel.None);
        if(appConfiguration == null) {

           //Configuration file not found, so throw an exception
           //TODO: thow an exception here
        } else {

           //Have Configuration, so work on the contents
           var fileEnvironment = appConfiguration.GetSection("fileEnvironment");
        }

No exception is thrown, but fileEnvironment is always null. Here is the file contents:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
   <configSections>
      <section name="fileEnvironment" type="System.Configuration.NameValueSectionHandler"/>
   </configSections>

   <fileEnvironment>
      <add key="DxStudioLocation" value="123456"/>
   </fileEnvironment>
</configuration>

Someone please lead me out of the wilderness. I also don't know how to write, or change, an entry in the NameValueCollection, after I get the contents of the section. Thanks