Get String From CodeBehind

Question

What is the difference between <%#...%> and <%=...%> ? For example I wanted to take the username of the logged in user and I tried with "<%# Membership.GetUser().UserName %>" but this didn't work. Then I tried with <%= Membership.GetUser().UserName %> and with this works. Why with the first try ( "<%# Membership.GetUser().UserName %>" ) didn't work but the second works fine ( <%= Membership.GetUser().UserName %> ) ?

With this code didn't work I can't get the field from " Membership.GetUser().UserName ":

<div id="profileHeader">
    <h1><%# Membership.GetUser().UserName %></h1>
</div>

With this code work I can get the field from " Membership.GetUser().UserName ":

<div id="profileHeader">
    <h1><%= Membership.GetUser().UserName %></h1>
</div>

Answer 1

<% %> : standard code-block

<%# %> : these servertags are for data-binding expressions.

<%= %> : those are for displaying variables.

Answer 2

Abbas is correct, here is the official wiki on the subject

Code render blocks , Data binding expression and Web Forms syntax in general.