Custom .Net Core policy using Func

ServiceExtensions.cs

public static void ConfigureAuthorization(this IServiceCollection services)
{
  services.AddAuthorization(options =>
  {
    options.AddPolicy("CanAccessSuperTopSecretArea", policy =>
      {
        context => context.User.HasClaim(claim => claim.Type == "TopSecretUser" || claim.Type == "OtherTopSecretUser" ||
        context.User.IsInRole("SupremeOverlord"))
      }
  }
}

TopSecretController.cs

public class TopSecretController : Controller
{
  [Authorize(Policy = "CanAccessSuperTopSecretArea")]
  public IActionResult Index()
  {
    return View();
  }
}

This authorization service extension (to avoid cluttering up Startup.cs) creates a policy called "CanAccessSuperTopSecretArea". A user in this policy must have the claim "TopSecretUser" OR "OtherTopSecretUser" OR is in the role "SupremeOverlord".