Unlocking the Mysteries of Data View Web Part XSL Tags – Part 4: xsl:with-param

Author: Marc D. Anderson
http://mdasblog.wordpress.com

<xsl:with-param>

You use this with <xsl:call-template> when you want to pass a value into a template, usually a value that varies.

Once you’ve laid down the foundation and framed the rooms with <xsl:template> and <xsl:call-template> (one of my goals in this series is to mix as many metaphors as possible), you can start building out. <xsl:with-param> is the way you can send variable information into a template for it to work with. Templates need some fodder to work with (see: another metaphor!) and <xsl:with-param> is a way to provide it.

<xsl:with-param> can only be used with <xsl:call-template>, so it passes the value into the template which you are calling just like you would do with a function or procedure in many other programming languages. If we look at the standard example again, you can see that some <xsl:call-template>s pass in parameters and some do not:

<XSL><xsl:stylesheet xmlns:x="<a href="http://www.w3.org/2001/XMLSchema">http://www.w3.org/2001/XMLSchema</a>" xmlns:d="<a href="http://schemas.microsoft.com/sharepoint/dsp">http://schemas.microsoft.com/sharepoint/dsp</a>" version="1.0" exclude-result-prefixes="xsl msxsl ddwrt" xmlns:ddwrt="<a href="http://schemas.microsoft.com/WebParts/v2/DataView/runtime">http://schemas.microsoft.com/WebParts/v2/DataView/runtime</a>" xmlns:asp="<a href="http://schemas.microsoft.com/ASPNET/20">http://schemas.microsoft.com/ASPNET/20</a>" xmlns:__designer="<a href="http://schemas.microsoft.com/WebParts/v2/DataView/designer">http://schemas.microsoft.com/WebParts/v2/DataView/designer</a>" xmlns:xsl="<a href="http://www.w3.org/1999/XSL/Transform">http://www.w3.org/1999/XSL/Transform</a>" xmlns:msxsl="urn:schemas-microsoft-com:xslt" xmlns:SharePoint="Microsoft.SharePoint.WebControls" xmlns:ddwrt2="urn:frontpage:internal">

<xsl:output method="html" indent="no"/>
<xsl:decimal-format NaN=""/>
<xsl:param name="dvt_apos">'</xsl:param>
<xsl:variable name="dvt_1_automode">0</xsl:variable>

<xsl:template match="/">
<xsl:call-template name="dvt_1"/>
</xsl:template>

<xsl:template name="dvt_1">
<xsl:variable name="dvt_StyleName">Table</xsl:variable>
<xsl:variable name="Rows" select="/dsQueryResponse/Rows/Row"/>
<table border="0" width="100%" cellpadding="2" cellspacing="0">
<tr valign="top">
<xsl:if test="$dvt_1_automode = '1'" ddwrt:cf_ignore="1">
<th width="1%" nowrap="nowrap"></th>
</xsl:if>
<th nowrap="nowrap">Title</th>
</tr>
<xsl:call-template name="dvt_1.body">
<xsl:with-param name="Rows" select="$Rows"/>
</xsl:call-template>
</table>
</xsl:template>

<xsl:template name="dvt_1.body">
<xsl:param name="Rows"/>
<xsl:for-each select="$Rows">
<xsl:call-template name="dvt_1.rowview"/>
</xsl:for-each>
</xsl:template>

<xsl:template name="dvt_1.rowview">
<tr>
<xsl:if test="position() mod 2 = 1">
<xsl:attribute name="class">ms-alternating</xsl:attribute>
</xsl:if>
<xsl:if test="$dvt_1_automode = '1'" ddwrt:cf_ignore="1">
<td width="1%" nowrap="nowrap">
<span ddwrt:amkeyfield="ID" ddwrt:amkeyvalue="ddwrt:EscapeDelims(string(@ID))" ddwrt:ammode="view"></span>
</td>
</xsl:if>
<td>
<xsl:value-of select="@Title"/>
</td>
</tr>
</xsl:template>
</xsl:stylesheet></XSL>

So you can see that the call to dvt_1.body passes the Rows parameter:

<xsl:call-template name="dvt_1.body">
<xsl:with-param name="Rows" select="$Rows"/>
</xsl:call-template>

and the call to the dvt_1 template passes no parameters:

<xsl:call-template name="dvt_1"/>

(There’s also a sort of "implied" parameter pass with <xsl:for-each>, but that will have to wait for the <xsl:for-each> installment.)

If you set some of the options on a DVWP, you may see a longer list of parameters passed into a template. For instance, if you turn on paging, you’ll see this in the call to dvt_body:

<xsl:call-template name="dvt_1.body">
<xsl:with-param name="Rows" select="$Rows"/>
<xsl:with-param name="FirstRow" select="1" />
<xsl:with-param name="LastRow" select="$LastRow - $FirstRow + 1" />
</xsl:call-template>

These extra values are required to make the paging work.  FirstRow is always set to 1, which isn’t very interesting, but LastRow is calculated to be the value of $LastRow – $FirstRow + 1.  Variables or parameters are referred to with a preceding dollar sign, and list columns with a preceding @ sign.  So $FirstRow would be a parameter or variable called FirstRow, where @FirstRow would be the value of a list column called FirstRow.

Frankly, if you try to trace through some of what SharePoint Designer creates along these lines, it may seem like total gobbledy-gook. This is primarily due to the fact that Designer needs to be "prepared" for the other options you might choose, and also due to the fact that it needs to add in XSL for boundary conditions that you may not think of. (First rows, last rows, etc.)

Next up: <xsl:param>. A value you’ve passed into a template with <xsl:with-param>. You need to have an <xsl:param> at the top of the template for each value you expect to be passed into it.

Author: Marc D. Anderson
http://mdasblog.wordpress.com

Marc D. Anderson is a Co-Founder and the President of Sympraxis Consulting LLC, based in Newton, MA.  He has over 25 years of experience as a technology consultant and line manager across a wide spectrum of industries and organizational sizes.  Marc has done extensive consulting on knowledge management and collaboration and what makes them actually work in practice.  Marc is a very frequent “answerer” on the MSDN SharePoint – Design and Customization forum.