Producing XHTML with ASP.NET


One common criticism of ASP.NET today is that the code it produces isn’t valid XHTML but
instead matches the HTML
4.01
Transitional doctype. XHTML is becoming increasingly prevalent on the web
due to its compatibility with XML (it’s just another XML schema) and ease of transformation
to support other uses (e.g. for accessibility).

It’s worth bearing in mind that when ASP.NET was first revealed at the PDC in 2000,
the biggest concern on everybody’s mind seemed to be compatibility with a wide range
of browsers. Netscape Navigator 4.x and Internet Explorer 3.x /
4.x were all still relatively common, with varying levels of support
for CSS and DHTML features. One of the big “wow” features of ASP.NET was that by flicking a
setting on the Document object
, you could change the way controls were laid out
on screen from using absolute co-ordinates in CSS to using nested tables (for the
broadest compatibility). Three years on from that initial PDC release, the vast majority
of browsers adhere very closely to the W3C specifications, and compatiblity concerns
have been replaced by concerns over conformance to new standards such as XHTML.

One piece of good news for those of you trying to retrofit ASP.NET to provide this
functionality is that the Whidbey release of ASP.NET will
generate XHTML 1.1-conformant pages
. In a year or so’s time, this will therefore
be an academic discussion.

In the meanwhile, I’ve recently seen two separate developments which should hopefully
reduce the pain of supporting XHTML within ASP.NET. Firstly, a colleague pointed me
at the following
article
on the ASP.NET
forums
, which is from a company who
are producing XHTML Strict 1.0 replacements of the standard server controls (thanks,
Kieran!).

Secondly, I lately came across a clever
trick for cleaning up the ViewState logic
emitted by ASP.NET to be XHTML compliant.
Well done to Charon for coming up with this trick. (Also see the posting
on Scott Galloway’s blog
 for another example).

Hopefuly these tips will save you some bother if you’re trying to get ASP.NET to do
what you want. Trying to look at all of this in a positive light, it’s tribute to
the extensibility and modularity of the ASP.NET architecture that it’s possible to
retrofit this kind of functionality into the engine – imagine trying to implement
these kinds of changes in ASP!


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