brianbolton.me

home

How to change variables in XSLT and Sharepoint

27 Oct 2010

In XSLT you cannot change the value of a xsl:variable once it has been set.

<xsl:variable name="counter" select="'1'"/>
<xsl:variable name="counter" select="'2'"/> <!-- does not work -->

This is less than desirable in many many scenarios. Incrementing a counter in a loop is the first place I needed it.

I wish you could avoid XSLT altogether but not so. Any developer programming in Sharepoint will eventually have to use XSLT for one thing or another. Lucky for you, there is a way to get around “write-once” variables in XSLT when used in Sharepoint.

Sharepoint comes with a custom namespace called DDWRT. Import this namespace into an XSLT file and you will have access to all of its functions. DDWRT has many functions. Check out the reference on MSDN for everything it can do.

The Setup

Add the ddwrt namespace to the xsl:stylesheet tag in the XSLT file.

xmlns:ddwrt="http://schemas.microsoft.com/WebParts/v2/DataView/runtime"

There might be other xmlns statements in the tag. Just add it last.

Set the Value

If you want to set the value of a variable, use this function:

ddwrt:SetVar('hasquery')

You cannot just call SetVar anywhere in your code. It needs to be inside XML. I will use xsl:value-of tag to wrap any set I make. It will look like this:

<xsl:value-of select="ddwrt:SetVar('counter','1')" />

  ## Get the Value

If you want to get the value of a variable, use this function:

ddwrt:GetVar(‘counter’)

GetVar always returns a string. So if you are doing a counter like I was, you’ll need to cast it to a number after you get the value. Use the number function built into XSLT to do the conversion. I use this one line to increment and then set the counter variable:

<xsl:value-of select="ddwrt:SetVar('counter',number(ddwrt:GetVar('counter')) + 1)" />