Send data fra javascript i postback til C#

JScript kode 

 <script type="text/javascript">
     var viewportwidth; 
     var viewportheight;
 
     //the more standards compliant browsers (mozilla/netscape/opera/IE7) use window.innerWidth and window.innerHeight
     if (typeof window.innerWidth != 'undefined') 
     {      
         viewportwidth = window.innerWidth,      
         viewportheight = window.innerHeight 
     }
 
     // IE6 in standards compliant mode (i.e. with a valid doctype as the first line in the document)
     else if (typeof document.documentElement != 'undefined' && typeof document.documentElement.clientWidth != 'undefined' && document.documentElement.clientWidth != 0)
     {       
         viewportwidth = document.documentElement.clientWidth,       
         viewportheight = document.documentElement.clientHeight 
     }
 
     // older versions of IE
     else 
     {       
         viewportwidth = document.getElementsByTagName('body')[0].clientWidth,       
         viewportheight = document.getElementsByTagName('body')[0].clientHeight 
     }
 
     document.write('<p>Your viewport width is ' + viewportwidth + 'x' + viewportheight + '</p>');
     
     </script>