Function Overloading

hi,

i am using a function named  "CheckID" for checking the validness of the querystring id received by the web page.
i have used function overloading here to allow addition of "where clause" in certain cases.
the function is working fine when id value is passed. ( eg: www.abc.com?id=1 and www.abc.com?id= )

but when the web page is accessed without id value (eg: www.abc.com), it gives a error message.
so i want that the function should work in both cases, whether a id value is passed on to the page or not.
 
    // Function to check valid id in the database table
    public static string CheckID(string id, string redirectURL, string redirectEmptyMsg, string redirectInvalidMsg, string dbTable, string dbTableColumn)
    {
        return CheckID(id, redirectURL, redirectEmptyMsg, redirectInvalidMsg, dbTable, d ...