<?pas
uses System.Net, System.Crypto;

var content := 'Immutable Content v1.0';
// Using SHA256 for ETag
var etag := '"' + HashSHA256.HashData(content) + '"';

// Check if client has a matching ETag
if WebRequest.Header['If-None-Match'] = etag then begin
   WebResponse.StatusCode := 304; // Not Modified
   exit;
end;

WebResponse.SetETag(etag);
WebResponse.ContentType := 'text/plain';
WebResponse.ContentData := content;
?>