How to check if query string exists

When retrieving a value from a query string in PHP you can add a check first to make sure the query string exists.



var $query_id;



if (isset($_GET["id"))

    $query_id = $_GET["id"];


How do I check to see if a query string exists before trying to use it in C#?



string queryID;



if (??????)

    queryID = HtmlPage.Document.QueryString["id"].ToString();

...