XPath(xml Path language)是一種處理XML文檔段的語言。XSLT(Extensible Stylesheet Language Transformations,可擴展樣式表語言轉換)使用XPath描述表達式和地址路徑控制節點選取。XSLT可以將XML轉換為各種格式，如HTML或其他格式。
    下面用一個郵件合并程序來簡要說明XPath的串函數。下面的XML文件中包含數據，XSLT文件中包含對郵件格式的定義。MSXML4.0對XML文檔應用樣式表，產生一個合并的郵件文本文檔。
XML文件 Letter.xml
<?xml version="1.0" encoding="UTF-8"?>
<Letter>

  <Date>July 17, 2002</Date>

  <To>
     <FirstName>Vicky</FirstName>
     <LastName>P</LastName>
     <Sex>Male</Sex>
  </To>

  <Address>
     <Line1>900 National Pkwy</Line1>
     <Line2>Suite 105</Line2>
     <City>Bellevue</City>
     <State>WA</State>
     <Zip>98007</Zip>
     <Country>USA</Country>
  </Address>

  <Subject>ESTATE OF JOHN DOE / FILE NO. 12345.6789</Subject>

  <Text>
     Please pay the PRoperty taxes as soon as possible.
  </Text>

  <Sender>
     <FirstName>John</FirstName>
     <LastName>M</LastName>
     <Title>Sr. Tax Consultant</Title>
  </Sender>

</Letter>

XSLT樣式表文檔 Letter.xsl
<?xml version='1.0' encoding="utf-8"?>
<xsl:stylesheet version="1.0"
      xmlns:xsl="

<xsl:output method="text" indent="yes"/>

<xsl:variable name="NL" select="'&#xA;'" />
<xsl:variable name="Para" select="concat($NL, $NL)" />

<xsl:template match="/">

   <xsl:value-of select="http://Date" />
   <xsl:value-of select="$Para" />

To,
<xsl:value-of select="concat(//To/FirstName, ' ', //To/LastName)" />
<xsl:value-of select="$NL" />

<xsl:value-of select="http://Address/Line1" />
<xsl:value-of select="$NL" />

<xsl:value-of select="http://Address/Line2" />
<xsl:value-of select="$NL" />

<xsl:value-of select="concat(//Address/City, ' ', //Address/State, ' ', //Address/Zip)" />
<xsl:value-of select="$NL" />

<xsl:value-of select="http://Address/Country" />
<xsl:value-of select="$Para" />

Regarding: <xsl:value-of select="http://Subject" />
<xsl:value-of select="$NL" />

Dear <xsl:if test="starts-with(//Sex, 'M')">Mr. </xsl:if><xsl:if test="starts-with(//Sex, 'F')">Miss </xsl:if>
<xsl:value-of select="concat(//To/FirstName, ' ', //To/LastName)" />,
<xsl:value-of select="$Para" />

<xsl:value-of select="http://Text" />
<xsl:value-of select="$Para" />
Sincerely,
<xsl:value-of select="$Para" />
<xsl:value-of select="concat(//Sender/FirstName, ' ', //Sender/LastName)" />
<xsl:value-of select="$NL" />
<xsl:value-of select="http://Sender/Title" />
</xsl:template>

</xsl:stylesheet>
 
    上面的樣式表舉例說明了concat和starts-with XPath串函數和怎樣在輸出文本中增加新行，還有定義和使用變量。
    下面是程序的執行結果。
    

1.VC6建立Win32控制臺應用程序。
2.在stdafx.h中添加下面的代碼：
   #include <TCHAR.H>
#include <stdio.h>
#include <time.h>
#import "msxml4.dll"
// If this import statement fails, you need to install MSXML 4.0 SP1 from:
//http://msdn.microsoft.com/downloads/sample.asp?url=/MSDN-FILES/027/001/766/msdncompositedoc.xml

#include <msxml2.h>
// If this include statement fails, you need to install MSXML 4.0 SP1 SDK from:
//http://msdn.microsoft.com/downloads/sample.asp?url=/MSDN-FILES/027/001/766/msdncompositedoc.xml
// You also need to add the include file and library search path
// to Visual C++'s list of directories (Tools > Options... > Directories).

using namespace MSXML2;

inline void EVAL_HR( HRESULT _hr )
   { if FAILED(_hr) throw(_hr); }
#define TEMP_SIZE  _MAX_PATH               // size of short buffer
static _TCHAR   szTemp[TEMP_SIZE];         // multipurpose buffer on stack
static DWord    dwLen;  

3.上面的代碼引入MSXML4類型庫，包含MSXML頭文件，檢查HRESULT值并聲明了一些全局變量。
4.main函數：
  int main(int argc, char* argv[])
{
 try
 {
  EVAL_HR(CoInitialize(NULL));

  // Make sure that MSXML 4.0 is installed
  if (!isMSXMLInstalled())
   return -1;

  // Make sure that XML and XSL file names are passed
  // as command line parameters
  if (argc < 3)
   // Show proper message here
   return -1;
 
  IXMLDOMDocument2Ptr pXMLDoc = NULL;
  IXMLDOMDocument2Ptr pXSLDoc = NULL;
 
  // Load the XML document
  if (loadDocument(pXMLDoc, argv[1], true))
  {
   // Load the stylesheet
   if (loadDocument(pXSLDoc, argv[2], false))
   {
    _ftprintf(stdout, pXMLDoc->transformNode(pXSLDoc));
   }
   else
   {
    printMSXMLError(pXSLDoc);
   }
  }
  else
  {
   printMSXMLError(pXMLDoc);
  }

 }
 catch(...)
 {//exception handling
 }
 
 _ftprintf(stdout, "/n/nPress Enter to continue...");
 getchar();
 CoUninitialize();
 return 0;
}

5.XML文件和XSLT樣式表文件名作為命令行參數傳遞給應用程序。主函數通過調用isMSXMLInstalled驗證    MSXML4.0是否安裝。接下來兩次調用loadDocument;先是加載XML文檔,然后是加載XSLT樣式表。 最后調用transformNode進行轉換。
6.本例代碼下載：http://www.perfectxml.com/CPPMSXML/downloads/20020716MailMerge.zip

譯自PerfectXML