I am trying to implement First Data Payment Gateway in my asp.net website.
I have done all things, now I can redirect to https://checkout.globalgatewaye4.firstdata.com/payment and Payment is done but then FirstData is redirecting to my site on Result.aspx page.
On that page how can I know that payment is done successfully or any error occurred etc. I know that it send response code in POST method but when come to my webpage it gives error like :
Server Error in '/' Application.
Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.
Any help ...
Thanks in advance..