Changes from version 2.x

The big change from version 2.0 was that, as of 2.1, the configuration is done by convention—that is, the process of adding appsettings.json JSON files (generic and optional per environment) and all that is hidden from the users.

This is defined in the WebHost.CreateDefaultBuilder method. You can, however, still build your own ConfigurationBuilder and add whatever you like to it. To do this, you call the ConfigureAppConfiguration method, as described in Chapter 1, Getting Started with ASP.NET Core, and illustrated in the following code block:

Host    .CreateDefaultBuilder(args)
    .ConfigureAppConfiguration(builder =>
    {
        var jsonSource = new JsonConfigurationSource { Path = 
            "appsettings.json" };
        builder.Add(jsonSource);
    })
    .ConfigureWebHostDefaults(builder =>
    {
        builder.UseStartup<Startup>();
    });

Or, if you just want to add a single entry to the configuration...