public static IBillingProcessor GetBillingProcessor(SupportedBillingProcessor processor)
        {
            if(_processors==null)
                _processors=new Dictionary<SupportedBillingProcessor,IBillingProcessor>();

            if (!_processors.ContainsKey(processor))
            {
                switch (processor)
                {
                    case SupportedBillingProcessor.Stripe:
                        _processors.Add(processor, new StripeBillingProcessor());
                        break;
                    default:
                        return null;
                }
            }

            return _processors[processor];
        }
 public static IBillingProcessor GetBillingProcessor(SupportedBillingProcessor processor)
 {
     return null;
 }