title: In ASP.NET, how to prevent tampering for a hidden field value
body: <p>I have a user control with a few dropdowns. I refill the dropdowns using ajax whenever one of them is changed based on the new selected value. </p>
  
  <p>The value of one of these dropdowns is the final value of the user control witch I want to bind to a data field. </p>
  
  <p>The problem is ASP.NET doesn't recognize values of dropdowns because they where generated in client-side. So I used a hidden field and whenever a value is selected in the dropdown I will put that value in the hidden field and I return the value of the hidden field as the user control value and everything works fine except </p>
  
  <p>I'm afraid that a user might tamper the value of that hidden field to an illegal value. 
  Is there a better way to do that?</p>