Did you remember to exclude namespaces from output?

When you work with XSLT, transforming XML to for instance the web in some CMS system, you might use some extra namespaces. Perhaps the CMS offers you some utilitiy namespace to handle relevant datastructure or procedures. You add them to your XSLT but perhaps you forgot to tell the XSLT processor not to add the namespaces to the output? Well I do some times…

Namespaces in a XSLT template

Adding namespaces to get extra features in your XSLT templates is easy. You may or may not think about it, but you will allways add at least one namespace “xsl”. Using Microsoft Visual Studio and selecting “New XSLT…” you will probertly also get a MS namespace like this: “msxsl”. I all happens in the beging of the template like this:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:msxsl="urn:schemas-microsoft-com:xslt"
  exclude-result-prefixes="msxsl "
  xmlns:cs="urn:custom-cs"
>

In the above example there are three namespaces:

xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:msxsl="urn:schemas-microsoft-com:xslt"
xmlns:cs="urn:custom-cs"

The first one “xsl” is telling the XSLT processor that we are using XSLT and that the we will be using the XSLT rules defined in 1999 by w3.org.

The next one “msxsl” addes MS custom features and will give you some nice new features, for instance functions to format dates (ms:format-date Function).

The last one I use for adding custom C# code in my XSLT. That is a very powerfull way of extending the XSLT processor with your own custom .NET code. But please take care when doing that!

Removing the namespace from the output

If you use custom namespaces you may end up with the namespaces added to the output elements. In the above code you may observe that there is an attribute “exclude-result-prefixes” on the xsl:stylesheet tag. It is used to tell the XSLT processor which namespaces should not be added to the output elements. I have added “msxsl” but not “cs”. I the example I use XSLT in Dynamicweb CMS to generate HTML, so I may get output looking like this:

<ul xmlns:cs="urn:custom-cs">

That is not what I wanted! To remove the “cs” namespace I simply need to modify the xsl:stylesheet attribute “exclude-result-prefix” to:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:msxsl="urn:schemas-microsoft-com:xslt"
  exclude-result-prefixes="msxsl cs"
  xmlns:cs="urn:custom-cs"
>

I have added the “cs” namespace, so I will now get a tag without the “cs” namespace in my HTML.

Using C# in XSLT – part 2: A remoteHTTP request

In this part of my C# in XSLT series of posts, I will show an example of making a basic remoteHTTP request from some inline C# code embedded inside a XSLT stylesheet. We will fetch a RSS feed from CNET.com and display it in a simpel UL list. The post XSLT transformations have been done using Microsoft Visual Studio.

A remoteHTTP request

You probertly know what a remoteHTTP request is, even if you have never heard about by that name. Every time you enter an URL you actually do a HTTP request. You point to an URL and get “something” back. In this post we will do just that, but from within some C# code being executed in the context of a XSLT transformation.

The result – effect – is that we can expand the XML which the XSLT can transform! Actually we only need a basic XML document to start up with – the actual XML is fetched from a remote site using the remoteHTTP request. So imagine that you have some XML which comes from a CMS system – say Dynamicweb CMS – you then need to fetch a RSS feed containing news from CNET.com and output an UL list with the news items on the webpage. We need some C# method to do the job for us…

The C# remoteHTTP method

Below you can see a screenshoot of the C# remoteHTTP method (you will find a link to a ZIP file containing the source code of this and the other files at the bottom of this page).

I will not say more about this code, other than I have added som basic Exception handling, returning a DOM tree with exception details (StackTrace, Message, Source, URL).

Here are some things I suggest when coding your C# code for use in XSLT:

a) In Visual Studio create a C# web project. In a “dummy” class add create the methodes and thereby getting intellicense and syntax check of the C# code.

b) Surround your code with try-catch error handling, things will go wrong at some time, so why not be prepared for it to happen?

c) Adding your XSLT file to the same project, you in practice have one structured container for both the syntax-validated methodes (classes at a later time!) and your XSLT stylesheets!

Preparing the XSLT stylesheet for inline C# code

To be able to make use of C# methodes from XSLT you need to do three things other than coding your C# code:

1) Add the namespaces and references making it possibel to execute C# code

We need to declare two namespaces for “urn:scemas-microsoft-com:xslt” and “urn:custom-cs”. At the same time I do not wish to return any elements with that namespace, so I add it to the “exclude-result-prefixes” of the stylesheet element.

2) Insert the C# code with the needed C# namespaces and assemblies

Within the msxsl namespace the “script” element is used. As you might guess C# is not the only supported language. I am not sure exactly which languages are supported, but jscript.net is supported. Normally I prefer javascript, but in this case I think that C# is best, as there are more help when doing the coding i the web project class. Actually I think that Microsoft is doing very little to support jscript.net.

3) Executing the C# and recieving the result

Above you see in line 60 how I call the remoteHTTP C# method:
cs:remoteHTTP('http://news.cnet.com/2547-1_3-0-20.xml')

In our example we define a variable called “feed”, and it will contain the XMLDocument which is located at the URL at http://news.cnet.com/2547-1_3-0-20.xml. It is a valid RSS 2.0 news feed, and the result will be a 100% valid XML DOM tree. With that we can do any kind of normal XSLT transformation – as you can see in line 75. Here I select the child element “rss” of within the variable ($feed). We have succeded in fetching an external RSS feed from within a XSLT stylesheet – allowing us in a very dynamic web to execute .NET code based on dynamic values!

As I mentioned in the first post “Using C# in XSLT transformations – Very strong tool!” I will be writing about the pros and cons when using this approach, so far I have been very positive, but ofcause nothing comes from free! There is a price to pay – more about that in a later post. For now: Enjoy this “new” way to enrich and add power to XSLT! I do!

You may download ZIP file using the link below, it contains a visual studio project which contains all the files you need, and a SIMPEL how-to page:

testXML.xml
Basic XML file which you can point to as your source XML file from Mictosoft Visual Studio when doing the transformation.
remoteHTTP.xslt
The XSLT stylesheet containing the C# code
remoteHTTP.htm
An example output of a transformation done in Mictosoft Visual Studio
remoteHTTP.cs
A C# class which I used for coding the C# code

Source files from this post

Using C# in XSLT transformations – Very strong tool!

When I build websites in Dynamicweb CMS I use XSLT templates. At the moment it is based on XSLT 1.0 which in its XSLT nature ofcause is much stronger than HTML based templates, but somehow limited compared to all the nice features which are defined in XSLT 2.0.

You may however extend to the extreme the facilities by using C# code in XSLT! I will start writing about the things I discover in this direction, writing about pros and cons. For now I wil not give any concrete examples, only mention that I have made an XSLT templates which gets a RSS feed (does a remoteHTTP request) and displays the transformed contents on a Dynamicweb page! Very cool! Something which I actually could not do without having to code my own Dynamicweb module!

It Rocks and I will start to think this into future templates – taking into account ofcause the pros and cons of that path!! This might just prove to be the best christmas present in the IT area of my life, this year!

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Category Archives: C# in XSLT