CustomDirectRouteProvider with inherited route prefix

CustomDirectRouteProvider .cs

    public class CustomDirectRouteProvider : DefaultDirectRouteProvider
    {
        protected override IReadOnlyList<IDirectRouteFactory> GetActionRouteFactories(HttpActionDescriptor actionDescriptor)
        {
            return actionDescriptor.GetCustomAttributes<IDirectRouteFactory>
            (inherit: true);
        }

        protected override string GetRoutePrefix(HttpControllerDescriptor controllerDescriptor)
        {
            var attributes = controllerDescriptor.GetCustomAttributes<IRoutePrefix>(inherit: true).ToArray();
            if (attributes == null)
            {
                return null;
            }
            var prefix = attributes[0];
            return prefix.Prefix;
        }
    }

if (attributes == null) is always false.

use

if (!attributes.Any())