public Driver(string env, string apiKey = null, string merchantKey = null) { if (String.IsNullOrEmpty(apiKey)) { throw new Exception("API Key is required"); } if (String.IsNullOrEmpty(merchantKey)) { throw new Exception("Merchant Key is required"); } Environments.validateEnvironment(env); this.Env = env; this.ApiKey = apiKey; this.MerchantKey = merchantKey; }