When should I use # and = in ASP.NET controls?
There are a couple of different 'bee-stings':
<%@- page directive<%$- resource access<%=- explicit output to page<%#- data binding<%--- server side comment block
Also new in ASP.Net 4:
<%:- writes out to the page, but with HTML encoded
Also new in ASP.Net 4.5:
<%#:- HTML encoded data binding
<%= %> is the equivalent of doing Response.Write("") wherever you place it.
<%# %> is for Databinding and can only be used where databinding is supported (you can use these on the page-level outside a control if you call Page.DataBind() in your codebehind)
Here's a great blog post by Dan Crevier that walks through a test app he wrote to show the differences.
In essence:
- 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.