Syntax:
extOptions.AddQueryStringParam(string name, string value);
The AddQueryStringParam adds a parameter with the given name and value to the query string of the URL used during the extended property detection redirect. This method is not generally necessary, but it can be useful if the original request had some non-parameter information, perhaps a header, that should be preserved.
Note: This method will add the specified parameter name and value even if a parameter with the same name already exists with another value. If you do not want the parameter to have two values (legal in HTTP and sometimes desirable), make sure you only call this method if the parameter is not already in the query string.