When should I use # and = in ASP.NET controls?

I have been using ASP.NET for years, but I can never remember when using the # and = are appropriate.

For example:

<%= Grid.ClientID %>

<%# Eval("FullName")%>

Can someone explain when each should be used so I can keep it straight in my mind? Is # only used in controls that support databinding?

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Answers:

Method 1

Method 2

Method 3

Answers:

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Method 1

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

Method 2

<%= %> 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)

Databinding Expressions Overview

Method 3

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.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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