CODEWITHSUNDEEP
asp.netdata-binding
y0mbo
y0mbo

Reputation: 4602

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 %>

or

<%# 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?

Upvotes: 27

Views: 4827

Answers (3)

Keith
Keith

Reputation: 155892

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

Upvotes: 44

Guy Starbuck
Guy Starbuck

Reputation: 21873

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.

Upvotes: 9

John Sheehan
John Sheehan

Reputation: 78152

<%= %> 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

Upvotes: 24

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