On our webserver we plan to move configuration to environment variables. We can set those environment variables in our Powershell Dsc script. But the website does not pick up the environment variables. There is an issue on github (#1864) that relates the LoadUserProfile setting of the application pool in IIS to the problem.

We deploy the website with IIS Web App Deployment Task in our release pipeline. In the Advanced tab > Additional AppCmd.exe Commands we can add the line to load the userprofile (and the environment variables)

set apppool "name_of_apppool" "-processmodel.loaduserprofile:true"
recycle apppool /apppool.name:name_of_apppool

Now the website loads the (proces/user/machine) environment variables into the configuration with the default code.

public Startup(IHostingEnvironment env)
{
  var builder = new ConfigurationBuilder()
        .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
        .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
        .AddEnvironmentVariables();
  Configuration = builder.Build();
}