title: ajax json call throws ClientScriptManager.RegisterForEventValidation error; how to register?
body: <p>I've been researching this like crazy, but I can't find a way to to get this error from triggering. I'm hoping someone here can help me.</p>
  
  <p>I have a drop down list object on my page that I'm creating as a server control, but which I'm dealing with entirely client-side at run time. The reason why I'm using a server control at all is because I need it to trigger an AJAX updatepanel elsewhere on my page. Anyway, this dropdown list starts blank, but gets populated with options by some jquery code based on user input. Up to this point there's no problem, but when the user makes a selection from this dropdown, I get the ClientScriptManager error. Selecting from this dropdown triggers an ajax json call to get data from the server.</p>
  
  <p>I'm registering all my client-side script files (including the one that contains the offending json call) with ClientScriptManager.RegisterClientScriptInclude. Registering the dropdown itself with RegisterforEventValidation doesn't work, because the dropdown has no options at load time.</p>
  
  <p>The application works in spite of this, but the error is defeating some enhancements I want to make, so I need to put this to rest. You can see the application (and view the error in your browser's debugging console) at <a href="https://www.heritagecutter.com/MillingCalc/" rel="nofollow">https://www.heritagecutter.com/MillingCalc/</a>; the dropdown your looking for is the one headed "Series", which will become active after you make selections in Material Group and Material Type above. The error appears after you select a series.</p>
  
  <p>Thanks in advance for any guidance.</p>