Difference between <%= and <%#

The ASP.NET syntax <%# %> is a shorthand convention that instructs the runtime to execute whatever is contained within and output the results “in Line”.

Difference between <%= and <%# -
From http://blogs.msdn.com/b/dancre/archive/2007/02/13/the-difference-between-lt-and-lt-in-asp-net.aspx

• The <%= expressions are evaluated at render time
  
• The <%# expressions are evaluated at DataBind() time and are not evaluated at all if DataBind() is not called.
  
• <%# expressions can be used as properties in server-side controls. <%= expressions cannot.