public static XafWebApiBuilder AddXafWebApi(
    this IServiceCollection services,
    IConfiguration configuration,
    Action<WebApiOptions> configureOptions
)

<ExtensionAttribute>
Public Shared Function AddXafWebApi(
    services As IServiceCollection,
    configuration As IConfiguration,
    configureOptions As Action(Of WebApiOptions)
) As XafWebApiBuilder

using MySolution.Module.BusinessObjects;
namespace MySolution.WebApi {
    public class Startup {
        public Startup(IConfiguration configuration) {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // ...
        public void ConfigureServices(IServiceCollection services) {
            // ...
            services.AddXafWebApi(Configuration, options => {
                options.BusinessObject<ApplicationUser>();
                options.BusinessObject<Contact>();
            })
            // in XPO applications, uncomment the following line
            // .AddXpoServices(); 
            // ...
        }
        // ...
    }
}