here my code that gives error-
OnClientClick='javascript:DragRevId(<%# XPath("ReservationId") %>);return false;'
It probably has something to do with the fact that XPath's use the '\' character. You'll need to escape that character if you want to use it with javascript.
Example: Node\Child --> Node\\Child
So, within ASP, do a String.Replace('\', "\\"); or something similar.
If this doesn't work you might want to consider posting the error that is thrown, and specifying if it is an ASP.Net error or a Javascript error.