adding attribute to the node

Part 1.

So let’s say if the country id is
equal to 32 then it should add
attribute country=32 to Employee node.

This transformation:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:template match="node()|@*">
  <xsl:copy>
   <xsl:apply-templates select="node()|@*"/>
  </xsl:copy>
 </xsl:template>

 <xsl:template match="Employee[countryid=32]">
  <Employee countryid="{countryid}">
   <xsl:apply-templates select="@*|node()"/>
  </Employee>
 </xsl:template>
</xsl:stylesheet>

when applied on the provided XML document:

<Employees>
    <Employee>
        <countryid>32</countryid>
        <id name="id">1</id>
        <firstname >ABC</firstname>
        <lastname >XYZ</lastname>
    </Employee>
    <Employee>
        <countryid>100</countryid>
        <id name="id">2</id>
        <firstname >ddd</firstname>
        <lastname >ggg</lastname>
    </Employee>
</Employees>

produces the wanted, correct result:

<Employees>
   <Employee countryid="32">
      <countryid>32</countryid>
      <id name="id">1</id>
      <firstname>ABC</firstname>
      <lastname>XYZ</lastname>
   </Employee>
   <Employee>
      <countryid>100</countryid>
      <id name="id">2</id>
      <firstname>ddd</firstname>
      <lastname>ggg</lastname>
   </Employee>
</Employees>

Explanation:

1. The identity rule is used to copy every node as-is. Using and overriding the identity rule (template) is the most fundamental and powerful XSLT design pattern.

2. There is only one template that overrides the identity rule for specific nodes — Employee elements that have a countryid child with string value (converted to number) 32. This template adds a countryid attribute to the Employee element and applies templates to resume the activity of the identity rule and copy everything else as-is.

Part 2.

Also can we pass countryid as comma
seprated values so that i can pass
32,100 and then it should add
attribute to all the matching nodes

This transformation:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:param name="pIds" select="'32,100'"/>

 <xsl:template match="node()|@*">
  <xsl:copy>
   <xsl:apply-templates select="node()|@*"/>
  </xsl:copy>
 </xsl:template>

 <xsl:template match="Employee">
  <Employee>
   <xsl:if test=
     "contains(concat(',',$pIds,','),
               concat(',',countryid,',')
               )">
    <xsl:attribute name="countryid">
      <xsl:value-of select="countryid"/>
    </xsl:attribute>
   </xsl:if>
   <xsl:apply-templates select="@*|node()"/>
  </Employee>
 </xsl:template>
</xsl:stylesheet>

when applied to the same XML document (above), produces the wanted, correct result:

<Employees>
   <Employee countryid="32">
      <countryid>32</countryid>
      <id name="id">1</id>
      <firstname>ABC</firstname>
      <lastname>XYZ</lastname>
   </Employee>
   <Employee countryid="100">
      <countryid>100</countryid>
      <id name="id">2</id>
      <firstname>ddd</firstname>
      <lastname>ggg</lastname>
   </Employee>
</Employees>