ELEMENT:  xsl:when
<xsl:choose>
  <xsl:when test="expression"> ... </xsl:when>
  ...
  <xsl:otherwise> ... <xsl:otherwise>
</xsl:choose>
 
The xsl:when element is a child of the xsl:choose element.
 
The xsl:choose element is used to make a choice when there are two or more possible courses of action. It provides a means for conducting multiple condition testing.
 
The xsl:choose element must contain one or more xsl:when elements and can contain only one optional xsl:otherwise element (which must occur after all of the xsl:when elements). If the xsl:choose element only contains one xsl:when element, then for all practical purposes, it behaves just like the xsl:if element. When faced with three or more choices, these elements behave similar to an if-then-else statement (or a Select Case) as found in numerous other computer languages.
 
The purpose of xsl:when element is to contain a Boolean expression that can be tested. The test must return a value of either true or false. Each xsl:when element is examined in the order of occurrence. If and when the conditions of the test expression are satisfied (returns True), the code contained in that element is executed. Then the xsl:choose element is automatically exited and all further xsl:when elements are ignored and they are not tested. The optional xsl:otherwise element is also automatically ignored.
 
If none of the test conditions in any xsl:when element is satisfied (all return False), then the xsl:otherwise element is automatically selected (if it is present) and the code associated with that element is executed. If there is no xsl:otherwise element, then the xsl:choose element is exited.
 
This element is not a self-closing tag. The separate closing element is mandatory.
 
test="expression"
 
The mandatory test attribute is a Boolean expression that is the test condition to be satisfied. A True signifies that the test conditions have been met. A False signifies that the test conditions have not been met. We use the DevGuru Staff List XML file for our example with the following header:
<?xml-stylesheet type="text/xsl" href="xslt_example_when.xsl"?>
 and we name it: xslt_example_when.xml
 
This example assigns font color based upon age.
 
Code for xslt_example_when.xsl:
 
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:template match="/">
<xsl:for-each select="devguru_staff/programmer">
<xsl:choose>
<xsl:when test="age &lt; 30">
<span style="color:red;">
NAME: <xsl:value-of select="name" /> AGE: <xsl:value-of select="age" />
</span>
</xsl:when>
<xsl:when test="age &lt; 40">
<span style="color:orange;">
NAME: <xsl:value-of select="name" /> AGE: <xsl:value-of select="age" />
</span>
</xsl:when>
<xsl:when test="age &lt; 50">
<span style="color:green;">
NAME: <xsl:value-of select="name" /> AGE: <xsl:value-of select="age" />
</span>
</xsl:when>
<xsl:when test="age &lt; 60">
<span style="color:blue;">
NAME: <xsl:value-of select="name" /> AGE: <xsl:value-of select="age" />
</span>
</xsl:when>
<xsl:otherwise>
<span style="color:black;">
NAME: <xsl:value-of select="name" /> AGE: <xsl:value-of select="age" />
</span>
</xsl:otherwise>
</xsl:choose>
<br />
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
 
Output:
 
Click to view output in separate window - requires Internet Explorer
 
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