Flat XML into tree with XSLT. Show one branch only - xslt

Question

I have flat xml structure, i need to convert into hierarchy. With the help of stackoverflow I was able to do it.
Question: Is it possible to show only one branch using the same flat structure?
Here is my xml and xsl files:
XML
<?xml version="1.0" encoding="utf-8"?>
<?xml-stylesheet type="text/xsl" href="Stack.xsl"?>
<Items>
<Item>
<Id>1</Id>
<ParentId>0</ParentId>
<Name>1</Name>
<SortOrder>0</SortOrder>
</Item>
<Item>
<Id>2</Id>
<ParentId>1</ParentId>
<Name>1.1</Name>
<SortOrder>0</SortOrder>
</Item>
<Item>
<Id>3</Id>
<ParentId>1</ParentId>
<Name>1.2</Name>
<SortOrder>0</SortOrder>
</Item>
<Item>
<Id>4</Id>
<ParentId>1</ParentId>
<Name>1.3</Name>
<SortOrder>0</SortOrder>
</Item>
<Item>
<Id>5</Id>
<ParentId>1</ParentId>
<Name>1.4</Name>
<SortOrder>0</SortOrder>
</Item>
<Item>
<Id>6</Id>
<ParentId>0</ParentId>
<Name>2</Name>
<SortOrder>0</SortOrder>
</Item>
<Item>
<Id>7</Id>
<ParentId>6</ParentId>
<Name>2.1</Name>
<SortOrder>0</SortOrder>
</Item>
<Item>
<Id>8</Id>
<ParentId>6</ParentId>
<Name>2.2</Name>
<SortOrder>0</SortOrder>
</Item>
<Item>
<Id>9</Id>
<ParentId>0</ParentId>
<Name>3</Name>
<SortOrder>0</SortOrder>
</Item>
<Item>
<Id>10</Id>
<ParentId>3</ParentId>
<Name>1.2.1</Name>
<SortOrder>0</SortOrder>
</Item>
<Item>
<Id>11</Id>
<ParentId>8</ParentId>
<Name>2.2.1</Name>
<SortOrder>0</SortOrder>
</Item>
<Item>
<Id>11</Id>
<ParentId>5</ParentId>
<Name>1.4.1</Name>
<SortOrder>0</SortOrder>
</Item>
</Items>
XSL
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns="http://www.w3.org/1999/xhtml">
<xsl:param name="SelectedId" select="'10'"/>
<xsl:key name="ChildNodes" match="/Items/Item" use="ParentId"/>
<xsl:template match="Items">
<ul>
<xsl:apply-templates select="Item[ParentId = 0]" />
</ul>
</xsl:template>
<xsl:template match="Item">
<li>
<xsl:choose>
<xsl:when test="Id = $SelectedId">
<b><xsl:value-of select="Name" /></b>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="Name" />
</xsl:otherwise>
</xsl:choose>
<xsl:variable name="Descendants" select="key ('ChildNodes', Id)" />
<xsl:if test="count ($Descendants) > 0">
<ul>
<xsl:apply-templates select="$Descendants" />
</ul>
</xsl:if>
</li>
</xsl:template>
</xsl:stylesheet>
Current output I have:
1
1.1
1.2
1.2.1
1.3
1.4
1.4.1
2
2.1
2.2
2.2.1
3
Desireable result example:
1
1.1
1.2
1.2.1
1.3
1.4
2
3

Answer 1

One way to do this is to make use of node-set function, which will require the use of an extension namespace in XSLT.
What you could do is that instead of outputing the Descendants variable directly as currently:
<ul>
<xsl:apply-templates select="$Descendants"/>
</ul>
You instead store the results in a variable
<xsl:variable name="list">
<ul>
<xsl:apply-templates select="$Descendants"/>
</ul>
</xsl:variable>
Then you can convert this 'result tree fragment' into a node-set, which you can then check for whether the selected element (held in a b element) exists. If so, you can then output it
<xsl:if test="exsl:node-set($list)//li[b]">
<xsl:copy-of select="$list"/>
</xsl:if>
Here is the full XSLT
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:exsl="urn:schemas-microsoft-com:xslt"
exclude-result-prefixes="exsl">
<xsl:output method="html"/>
<xsl:param name="SelectedId" select="'10'"/>
<xsl:key name="ChildNodes" match="/Items/Item" use="ParentId"/>
<xsl:template match="Items">
<ul>
<xsl:apply-templates select="Item[ParentId = 0]"/>
</ul>
</xsl:template>
<xsl:template match="Item">
<li>
<xsl:choose>
<xsl:when test="Id = $SelectedId">
<b>
<xsl:value-of select="Name"/>
</b>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="Name"/>
</xsl:otherwise>
</xsl:choose>
<xsl:variable name="Descendants" select="key ('ChildNodes', Id)"/>
<xsl:if test="count ($Descendants) > 0">
<xsl:variable name="list">
<ul>
<xsl:apply-templates select="$Descendants"/>
</ul>
</xsl:variable>
<xsl:if test="exsl:node-set($list)//li[b]">
<xsl:copy-of select="$list"/>
</xsl:if>
</xsl:if>
</li>
</xsl:template>
</xsl:stylesheet>
When applied to your sample XML, the following is output
<ul>
<li>1
<ul>
<li>1.1</li>
<li>1.2
<ul>
<li>
<b>1.2.1</b>
</li>
</ul></li>
<li>1.3</li>
<li>1.4</li>
</ul></li>
<li>2</li>
<li>3</li>
</ul>
Note, because I am using Microsoft XML here, the extension namespace is "urn:schemas-microsoft-com:xslt". For other processors, you will probably have to use "http://exslt.org/common"