expr Property

[Script]

Script Syntax

strExpression = objXMLDOMSelection.expr;
objXMLDOMSelection.expr = strExpression;

Example

var xmlDoc = new ActiveXObject("Msxml2.DOMDocument.4.0");
var selection;
xmlDoc.loadXML("<Customer><Name>Microsoft</Name></Customer>");
xmlDoc.setProperty("SelectionLanguage", "XPath");
selection = xmlDoc.selectNodes("Customer/Name");
alert(selection.expr + " -- " + selection.item(0).xml);

This displays "Customer/Name -- <Name> Microsoft</Name>".

selection.expr = "/Customer";

The selection is immediately refreshed with a list corresponding to the new expression.

alert(selection.expr + " -- " + selection.item(0).xml);

This displays "/Customer -- <Customer><Name> Microsoft</Name></Customer>".

[Visual Basic]

Visual Basic Syntax

strExpression = objXMLDOMSelection.expr
objXMLDOMSelection.expr = strExpression

Example

Dim xmlDoc As New Msxml2.DOMDocument40
Dim selection As Msxml2.IXMLDOMSelection

xmlDoc.loadXML ("<Customer><Name>Microsoft</Name></Customer>")
xmlDoc.setProperty "SelectionLanguage", "XPath"
Set selection = xmlDoc.selectNodes("Customer/Name")
MsgBox selection.expr + " -- " + selection.Item(0).xml

This displays "Customer/Name -- <Name> Microsoft</Name>".

selection.expr = "/Customer"

The selection is immediately refreshed with a list corresponding to the new expression.

MsgBox selection.expr + " -- " + selection.Item(0).xml

This displays "/Customer -- <Customer><Name> Microsoft</Name></Customer>".

[C/C++]

C/C++ Syntax

HRESULT get_expr(BSTR* expression);
HRESULT put_expr(BSTR expression);

Parameters

expression [out, retval][in]

A string specifying the expression to be returned or set. This string is an XPath expression only if the setProperty method has set the SelectionLanguage internal property (flag) to "XPath". Otherwise, this string is an XSL Patterns query.

C/C++ Return Values

S_OK

The value returned if method is successful.

E_FAIL and formatted error message through IErrorInfo if expression is invalid.

Example

The following C/C++ example shows the resetting of the selected nodes list if the expr property is changed.

#import "msxml3.dll"
using namespace MSXML2;

#define CHECK_AND_RELEASE(pInterface)  \
if(pInterface) \
   {\
pInterface->Release();\
pInterface = NULL;\
   }\

#define RELEASE(pInterface)  \
   {\
pInterface->Release();\
pInterface = NULL;\
   }\

BOOL DOMSelectionExprDemo()
{
   BOOL bResult = FALSE;
   short sResult = FALSE;
   long lvalue;
   IXMLDOMSelection *pIXMLDOMSelection=NULL;
   IXMLDOMDocument2 *pIXMLDOMDocument2=NULL;
   HRESULT hr;
   BSTR bstrValue;

   try
   {
      hr=CoCreateInstance(CLSID_DOMDocument, NULL, CLSCTX_SERVER, 
         IID_IXMLDOMDocument2, (LPVOID*)(&pIXMLDOMDocument2));
      SUCCEEDED(hr) ? 0 : throw hr;

      if(pIXMLDOMDocument2)
      {
         hr=pIXMLDOMDocument2->put_async(VARIANT_FALSE);
         if(SUCCEEDED(hr))
         {
            hr=pIXMLDOMDocument2->load(_variant_t( 
               _T("d:\\inetpub\\wwwroot\\sample.xml")), &sResult);
            if(SUCCEEDED(hr) && (sResult==VARIANT_TRUE))
            {
               hr=pIXMLDOMDocument2->selectNodes( 
                  _T("*/BOOK[TITLE='Cosmos']"), 
                  (IXMLDOMNodeList**)&pIXMLDOMSelection);
               if(SUCCEEDED(hr))
               {
                  if(SUCCEEDED(hr) && pIXMLDOMSelection)
                  {
                     hr = pIXMLDOMSelection->get_expr(&bstrValue);
                     if(SUCCEEDED(hr))
                     {
                        ::MessageBox(NULL, bstrValue, _T("Current 
                           Expression"), MB_OK);
                        bResult=TRUE;
                        hr = pIXMLDOMSelection->get_length(&lvalue);
                        hr = pIXMLDOMSelection->put_expr(_T("*/BOOK"));
                        hr = pIXMLDOMSelection->get_length(&lvalue);
                     }
                     RELEASE(pIXMLDOMSelection);
                  }
               }
            }
         }
         RELEASE(pIXMLDOMDocument2);
      }
   }
   catch(...)
   {
      CHECK_AND_RELEASE(pIXMLDOMSelection);
      CHECK_AND_RELEASE(pIXMLDOMDocument2);
      DisplayErrorToUser();
   }
   return bResult;
}

File Name: d:\\inetpub\\wwwroot\\sample.xml

<?xml version='1.0'?>
<COLLECTION xmlns:dt="urn:schemas-microsoft-com:datatypes">
   <DATE dt:dt="datetime">1998-10-13T15:56:00</DATE>
   <BOOK>
      <TITLE>Cosmos</TITLE>
      <AUTHOR>Carl Sagan</AUTHOR>
      <PUBLISHER>Ballantine Books</PUBLISHER>
   </BOOK>
   <BOOK>
      <TITLE>Catwings</TITLE>
      <AUTHOR>Ursula K. Le Guin</AUTHOR>
      <PUBLISHER>Scholastic</PUBLISHER>
   </BOOK>
</COLLECTION>

Output (in a message box)

The first message box will display "1".

The second message box will display "2". When the expression changes, the nodes in the selection are recomputed using the new expression. No changes are made to the context property.