Automatically get ClientcustomerId from adwords api version v201601

I'm using adwords api version v201509 . now i want to migrate this version to v201601.

Here i'm getting error while accessing customer id and name.

Here is my code. 

            AdWordsUser adWordsUser = new AdWordsUser();

            (adWordsUser.Config as AdWordsAppConfig).DeveloperToken = Globals.ThisAddIn.AdWordsDeveloperToken;

            (adWordsUser.Config as AdWordsAppConfig).OAuth2RefreshToken = refreshtoken;

            (adWordsUser.Config as AdWordsAppConfig).OAuth2ClientId = Globals.ThisAddIn.AdWordsClientId;

            (adWordsUser.Config as AdWordsAppConfig).OAuth2ClientSecret = Globals.ThisAddIn.AdWordsClientSecretId;

 var customerService = (CustomerService)adWordsUser.GetService(AdWordsService.v201509.CustomerService);

            Customer customer = new Customer();

            customer = customerService.get();

this code works fine , and i'm getting customer details from customerservice.

the problem is with v201601, i updated same here, here i'm getting error like client_customer_id_invalid.

Can anyone suggest me , how , i solve the issue.

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