javascript renable asp Button on Upload of file

$(document).ready(function () {
   $('#<%= YourFileUploadControl.ClientID %>').change( function(){
      if ( $('#<%= YourFileUploadControl.ClientID %>').val() <> '' ){
         $('#<%= YourButtonControl.ClientID %>').removeAttr('disabled');
      }
      else {
         $('#<%= YourButtonControl.ClientID %>').attr('disabled', 'disabled');
      }
    });
});