There are 3 main differences:
1. <%= expressions are evaluated at render time
2. <%# expressions are evaluated at DataBind() time and are not evaluated at all if DataBind() is not called.
3. <%# expressions can be used as properties in server-side controls. <%= expressions cannot.
Read this if you want to know how to get a correct reply for your question:
^^Took that from planoie's profile^^
^^Modified text taken from gbianchi profile^^
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