title: ASP.NET Payment Form Submission Need Guidance
body: <p>Guys, I apologize me if the question is less organized and less clear. I am in hurry :(</p>
  
  <p>My web app has payment form that need to be submitted to another ASP.NET page (lets call it <a href="http://vendor.com/getpay.aspx" rel="nofollow">http://vendor.com/getpay.aspx</a>)
  residing on another server.</p>
  
  <p>That page will do some mumbo-jumbo works and then redirects it to the acutal 
  payment gateway site.</p>
  
  <p>when i post my payment form to getpay.aspx via simple HTML form, it works and redirects fine.</p>
  
  <p>if i change the form and its hidden inputs to server side controls, it doesn't work. their page is throwing viewstate exception.</p>
  
  <ol>
  <li>I need the form hidden inputs to be server controls so that i can bind some values generated by my code behind.(i think i can do this like the classic asp way using &lt;%= %>, but it is like going back in standard!)</li>
  <li>I tried HttpWebRequest in the code behind, it posts the form but the browser doesn't redirect to Payment Gateway page. </li>
  <li>I am posting the payment info over non https, how can i prevent the user tampering with the posted data?.</li>
  <li>I want to validate the payment form in the backend then post it, i couldn't trust the user input data.</li>
  <li>Also the result was returned to my redirect page with query strings appended. It is also happening over the non https. 
  how much i can trust this redirect data?</li>
  </ol>
  
  <p>Thx much </p>