Startup.cs

// OLD WAY FROM ASP.NET CORE PRIOR TO 3.0!!!!!!!!!
public class Startup
{
    // Other Startup code omitted     
    public void ConfigureServices(IServiceCollection services)
    {
        // OLD WAY FROM ASP.NET CORE PRIOR TO 3.0!!!!!!!!!
        services.AddMvc(options =>
        {
            var policy = new AuthorizationPolicyBuilder()
                .RequireAuthenticatedUser()
                .Build();
            options.Filters.Add(new AuthorizeFilter(policy));
        });
        
        // Other service registrations omitted
    }
}