What is a good method for preventing a user from submitting a form twice?

c# asp.net-mvc form-submit
CloudMeta picture CloudMeta · Jan 21, 2010 · Viewed 14.1k times · Source

I have a purchase page and I don't want the user to be able to refresh the page and resubmit the form once they get to the 'order complete' page because it automatically sets them up in our system via database values and charges their card via paypal (only want these to happen ONCE)... I have seen some sites that say 'Don't hit refresh or you will get charged twice!' but that is pretty lame to leave it open to possibility, what's a good way to only allow it to be submitted once or prevent them from refreshing, etc?

PS: I saw a few similar questions: PHP: Stop a Form from being accidentally reprocessed when Back is pressed and How do I stop the Back and Refresh buttons from resubmitting my form? but found no satisfactory answer... an ASP.NET MVC specific answer would be ideal too if there is a mechanism for this.

EDIT: Once they click submit it POSTS to my controller and then the controller does some magic and then returns a view with an order complete message, but if I click refresh on my browser it does the whole 'do you want to resend this form?' that is bad...

Answer

D'Arcy Rittich picture D'Arcy Rittich · Jan 21, 2010

The standard solution to this is the POST/REDIRECT/GET pattern. This pattern can be implemented using pretty much any web development platform. You would typically:

  • Validate submission after POST
  • if it fails re-render the original entry form with validation errors displayed
  • if it succeeds, REDIRECT to a confirmation page, or page where you re-display the input - this is the GET part
  • since the last action was a GET, if the user refreshes at this point, there is no form re-submission to occur.

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