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Selects a list of nodes matching the XPath expression. Any prefixes found in the XPath expression are resolved using the supplied XmlNamespaceManager.
Namespace: System.Xml
Assembly: System.Xml (in System.Xml.dll)
Public Function SelectNodes ( _ xpath As String, _ nsmgr As XmlNamespaceManager _ ) As XmlNodeList
public XmlNodeList SelectNodes( string xpath, XmlNamespaceManager nsmgr )
public:
XmlNodeList^ SelectNodes(
String^ xpath,
XmlNamespaceManager^ nsmgr
)
member SelectNodes : xpath:string * nsmgr:XmlNamespaceManager -> XmlNodeList
Parameters
- xpath
- Type: System.String
The XPath expression.
- nsmgr
- Type: System.Xml.XmlNamespaceManager
An XmlNamespaceManager to use for resolving namespaces for prefixes in the XPath expression.
Return Value
Type: System.Xml.XmlNodeListAn XmlNodeList containing a collection of nodes matching the XPath query.
| Exception | Condition |
|---|---|
| XPathException |
The XPath expression contains a prefix which is not defined in the XmlNamespaceManager. |
XPath expressions can include namespaces. Namespace resolution is supported using the XmlNamespaceManager. If the XPath expression includes a prefix, the prefix and namespace URI pair must be added to the XmlNamespaceManager.
Note
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|---|
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If the XPath expression does not include a prefix, it is assumed that the namespace URI is the empty namespace. If your XML includes a default namespace, you must still add a prefix and namespace URI to the XmlNamespaceManager; otherwise, you will not get any nodes selected. For more information, see Select Nodes Using XPath Navigation. |
For example, if you had the following XML:
<bookstore xmlns="http://www.lucernepublishing.com">
<book>
<title>Pride And Prejudice</title>
</book>
</bookstore>
The following C# code selects all book nodes:
XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);
nsmgr.AddNamespace("ab", "http://www.lucernepublishing.com");
XmlNodeList nodelist = doc.SelectNodes("//ab:book", nsmgr);
Note
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|
A common issue when formulating XPath expressions is how to include a single quote (') or double quote (") in the expression. If you have to search for a value that includes a single quote, you must enclose the string in double quotes. If you need to search for a value that includes a double quote, you must enclose the string in single quotes. |
For example, suppose you have the following XML:
<bookstore xmlns="http://www.lucernepublishing.com">
<book>
<title>'Emma'</title>
</book>
</bookstore>
The following Visual Basic code selects an element that contains single quotes:
Dim nsmgr As XmlNamespaceManager = New XmlNamespaceManager(doc.NameTable)
nsmgr.AddNamespace("ab", "http://www.lucernepublishing.com")
nodeList = root.SelectNodes("//ab:book[contains(ab:title,""'Emma'"")]", nsmgr)
This method is a Microsoft extension to the Document Object Model (DOM).
The XmlNodeList object returned by this method will be valid while the underlying document remains unchanged. If the underlying document changes, unexpected results may be returned (no exception will be thrown).
The following example displays the values of each of the ISBN attributes.
Imports System Imports System.IO Imports System.Xml public class Sample public shared sub Main() Dim doc as XmlDocument = new XmlDocument() doc.Load("booksort.xml") 'Create an XmlNamespaceManager for resolving namespaces. Dim nsmgr as XmlNamespaceManager = new XmlNamespaceManager(doc.NameTable) nsmgr.AddNamespace("bk", "urn:samples") 'Select and display the value of all the ISBN attributes. Dim nodeList as XmlNodeList Dim root as XmlElement = doc.DocumentElement nodeList = root.SelectNodes("/bookstore/book/@bk:ISBN", nsmgr) Dim isbn as XmlNode for each isbn in nodeList Console.WriteLine(isbn.Value) next end sub end class
using System; using System.IO; using System.Xml; public class Sample { public static void Main() { XmlDocument doc = new XmlDocument(); doc.Load("booksort.xml"); //Create an XmlNamespaceManager for resolving namespaces. XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable); nsmgr.AddNamespace("bk", "urn:samples"); //Select and display the value of all the ISBN attributes. XmlNodeList nodeList; XmlElement root = doc.DocumentElement; nodeList = root.SelectNodes("/bookstore/book/@bk:ISBN", nsmgr); foreach (XmlNode isbn in nodeList){ Console.WriteLine(isbn.Value); } } }
#using <System.Xml.dll> using namespace System; using namespace System::IO; using namespace System::Xml; using namespace System::Collections; int main() { XmlDocument^ doc = gcnew XmlDocument; doc->Load( "booksort.xml" ); // Create an XmlNamespaceManager for resolving namespaces. XmlNamespaceManager^ nsmgr = gcnew XmlNamespaceManager( doc->NameTable ); nsmgr->AddNamespace( "bk", "urn:samples" ); // Select and display the value of all the ISBN attributes. XmlNodeList^ nodeList; XmlElement^ root = doc->DocumentElement; nodeList = root->SelectNodes( "/bookstore/book/@bk:ISBN", nsmgr ); IEnumerator^ myEnum = nodeList->GetEnumerator(); while ( myEnum->MoveNext() ) { XmlNode^ isbn = safe_cast<XmlNode^>(myEnum->Current); Console::WriteLine( isbn->Value ); } }
The example uses the file, booksort.xml, as input.
<?xml version="1.0"?>
<!-- A fragment of a book store inventory database -->
<bookstore xmlns:bk="urn:samples">
<book genre="novel" publicationdate="1997" bk:ISBN="1-861001-57-8">
<title>Pride And Prejudice</title>
<author>
<first-name>Jane</first-name>
<last-name>Austen</last-name>
</author>
<price>24.95</price>
</book>
<book genre="novel" publicationdate="1992" bk:ISBN="1-861002-30-1">
<title>The Handmaid's Tale</title>
<author>
<first-name>Margaret</first-name>
<last-name>Atwood</last-name>
</author>
<price>29.95</price>
</book>
<book genre="novel" publicationdate="1991" bk:ISBN="1-861001-57-6">
<title>Emma</title>
<author>
<first-name>Jane</first-name>
<last-name>Austen</last-name>
</author>
<price>19.95</price>
</book>
<book genre="novel" publicationdate="1982" bk:ISBN="1-861001-45-3">
<title>Sense and Sensibility</title>
<author>
<first-name>Jane</first-name>
<last-name>Austen</last-name>
</author>
<price>19.95</price>
</book>
</bookstore>
.NET Framework
Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0.NET Framework Client Profile
Supported in: 4, 3.5 SP1Windows 8 Consumer Preview, Windows Server 8 Beta, Windows 7, Windows Server 2008 SP2, Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Note