Editing Xmls with intellisense in Visual Studio

Am I the last person in the world to realise that? hopefully not!...

...but I've just realised today that if you edit an xml file in visual studio and you have the schema of the xml you're editing open in another tab it will recognise it (as soon as you type the root node and namespace) and will provide intellisense.

I knew you could tell it to use a schema, but I did not realise it will automatically include opened documents. brilliant feature!

processing xml in two phases in xsl

Over the last few months I've been involved in the development of quite a few xsl scripts; one requirement that kept coming up and, as I'm not an xsl expert I always thought is impossible, was to perform what I would describe as - two phase parsing -where we run one bit of xsl to create an interim xml only to run another bit of xsl on it to get the results we want.

Here's an example of this requirement, I hope I can describe it in a way that makes sense:

Imagine you have two xml messages that are linked - one has a list of items, and the other their prices, something like this:

<?xml version="1.0" encoding="utf-8"?>
<ns0:Root xmlns:ns0="http://schemas.microsoft.com/BizTalk/2003/aggschema">
 <InputMessagePart_0>
  <items>
   <item type="book" name="book1" barcode="12"/>
   <item type="book" name="book2" barcode="34"/>
   <item type="cd" name="cd1" barcode="56"/>
   <item type="cd" name="cd2" barcode="78"/>
  </items>
 </InputMessagePart_0>
 <InputMessagePart_1>
  <prices>
   <price price="10.5">
    <barcodes>
     <barcode>12</barcode>
    </barcodes>
   </price>
   <price price="24.70">
    <barcodes>
     <barcode>34</barcode>
    </barcodes>
   </price>
   <price price="56.20">
    <barcodes>
     <barcode>56</barcode>
    </barcodes>
   </price>
   <price price="90.14">
    <barcodes>
     <barcode>78</barcode>
    </barcodes>
   </price>
  </prices>
 </InputMessagePart_1>
</ns0:Root>

(This might not make much sense as an example, but trust me - it represents a real world scenario that does, also - note the structure we've used to get both messages is the one BizTalk uses to get multiple message parts into a map)

Now - what we want to get in the end is this:

<itemTotals>
 <itemType>
  <type>book</type>
  <total>35.2</total>
 </itemType>
 <itemType>
  <type>cd</type>
  <total>146.34</total>
 </itemType>
</itemTotals>

As far as I can tell, getting from #1 to #2 in one go is not possible (but I'd love to hear otherwise), so our only conclusion was that we need to go through two stages in processing - in the first one we would de-normalise the two messages to one flattened xml, and in the second we will get the distinct types and sums.

So, to tackle the first stage we wrote a simple xsl that creates the interm xml we wanted - the output looks like this:

<itemTotals>
 <item type="book" total="10.5" />
 <item type="book" total="24.70" />
 <item type="cd" total="56.20" />
 <item type="cd" total="90.14" />
</itemTotals>

than, we put this xsl script inside a variable declaration; our xsl now looks like this:

<xsl:template match="/">
 <xsl:variable name="items">
  <xsl:for-each select="/*[local-name()='Root' and namespace-uri()='http://schemas.microsoft.com/BizTalk/2003/aggschema']/*[local-name()='InputMessagePart_0' and namespace-uri()='']/*[local-name()='items' and namespace-uri()='']/*[local-name()='item' and namespace-uri()='']">
   <xsl:element name="item">
    <xsl:attribute name="type">
     <xsl:value-of select="@type"/>
    </xsl:attribute>
    <xsl:variable name="barcode" select="@barcode"/>
    <xsl:attribute name="total">
     <xsl:value-of select="/*[local-name()='Root' and namespace-uri()='http://schemas.microsoft.com/BizTalk/2003/aggschema']/*[local-name()='InputMessagePart_1' and namespace-uri()='']/*[local-name()='prices' and namespace-uri()='']/*[local-name()='price' and namespace-uri()='' and child::*/child::*=$barcode]/@price"/>
    </xsl:attribute>
   </xsl:element>
  </xsl:for-each>
 </xsl:variable>
</xsl:template>

(sorry for the long xpaths, we've had to make them "BizTalk friendly"...)

That gives us the interm xml we need to work on and is one of two "magic" bits to get this working - we did not realise up until now that we could put whole chunk of xml into a variable, and that we could use xsl to create that xml in a variable.

Having the xml in a variable, we hoped, would allow us to run another set of xsl on it before outputing it as the script's result. but there was one additional maginc point missing - as the variable was not retrieved in the normal <variable name="myVar" select="someXPath"/> it's contents is not considered a node-set but just a literal that looks like a node-set and as such we could not use this variable in further xpaths in the script.

Thankfully, Microsoft has provided a function to convert one to the other, so we had the next line of xsl to our script:

 <xsl:variable name="itemsNodeSet" select="msxsl:node-set($items)"/>

we had to add the namespace declaratino for msxsl in the stylesheeet declaraion -

       xmlns:msxsl="urn:schemas-microsoft-com:xslt"

Now that we have the interm xml in a variable, and is considered a node-set we could simply run the last bit of xsl we need to get the totals:

(the for each uses another nice technique we use in xsl to get a distinct list of items in a list)

 <xsl:for-each select="$itemsNodeSet/*[not(@type=preceding-sibling::*/@type)]">
  <itemType>
   <type>
    <xsl:value-of select="@type"/>
   </type>
   <total>
    <xsl:variable name="type" select="@type"/>
    <xsl:value-of select="sum($itemsNodeSet/item[@type=$type]/@total)"/>
   </total>
  </itemType>
 </xsl:for-each>

and voila! - the output is exactly what we wanted!

Passing xml between xsl and a helper method

I'm using a lot of custom xsl. in fact - most of my transformations are custom xsl files, skipping the mapper altogether.

In that, I'm also quite frequently using helper classes in assemblies called directly from the xsl, on which I have posted before.

Mostly I'm passing simple values between the two such as strings and ints, but every now and then I need to pass a whole xml struture between them - it might be a node-set from the xsl that needs to be processed by the helper method, it might be that the method returns an xml fragment the xsl needs to then iterate on or, most likely, it will be both.

The way to do it is quite simply to use the XPathNodeIterator class in the System.Xml.XPath namespace.

I did not know about this class until I had to do this bit, so it has to be worth posting (for myself if not for anyone else).

To demonstrate it's use I've create a helper method as follwos -

public XPathNodeIterator processXml(XPathNodeIterator nodeset)

{

nodeset.MoveNext();

XPathNavigator nav = nodeset.Current;

XPathNodeIterator i = nav.Select("//*");

return i;

}

As you can see this method doesn't really do much, but it already demonstrates how to receive an xml node-set and how to return one.

the helper method can work with the following xsl -

<xsl:variable name="MyNodeSet" select="<some xpath>"/>

<xsl:variable name="HelperResult" select="helpers:processXml($MyNodeSet)"/>

<xsl:value-of select="$HelperResult/<some other xpath>"/>


The next challange was how to create a brand new XPathNodeIterator, here's one way (assuming xmlDoc is an XmlDocument that contains the xml you need to return -

XPathNavigator xPathNav;

xPathNav = xmlDoc.CreateNavigator();

xPathNav.MoveToRoot();

XPathExpression xPathExpr = xPathNav.Compile("");

XPathNodeIterator xPathNodI = xPathNav.Select(xPathExpr);