Last updated December 13 2025.
This post covers classic ASP.NET WebForms syntax. Modern .NET development typically uses Razor syntax in ASP.NET Core MVC, Razor Pages, or Blazor.
ASPX in-page expressions are, if you don’t know what to call them, nearly impossible to search. So on the off chance that this helps somebody, here are some search-friendly terms that might one day get crawled; (less than percent hash), (less than percent equals), (in-page expressions), (data binding), (data bound), (bee strings), (asp.net server tags), (code render blocks)
<% %> is for inline code (especially logic flow)<%$ %> is for evaluating expressions (like resource variables)<%@ %> is for Page directives, registering assemblies, importing namespaces, etc.<%= %> is short-hand for Response.Write (discussed here)<%# %> is used for data binding expressions.<%: %> is short-hand for Response.Write(Server.HTMLEncode()) in ASP.net 4.0+<%-- --%> is for server-side commentsThis information is replicated from the following sources StackOverflow post, Dan Crevier’s blog and in an MSDN article. No excuses then.