在MVC。net中，PayPal express checkout响应作为html返回

I had test application integrated with Paypal express checkout and it was running fine. But now there seems some issue. After successful payment on paypal when my IPN handler check for response paypal returns response as html page instead of "VERIFIED" OR "INVALID" and because of this I'm not able to verify the payment. Is there any change in Paypal recently for express checkout? Below is complete codeI had test application integrated with Paypal e