SelectSingleNode(System.String,System.Xml.XmlNamespaceManager)

Selects the first XmlNode that matches the XPath expression. Any prefixes found in the XPath expression are resolved using the supplied System.Xml.XmlNamespaceManager.

Syntax

public XmlNode SelectSingleNode (string xpath, XmlNamespaceManager nsmgr)

Parameters

xpath
The XPath expression.
nsmgr
An System.Xml.XmlNamespaceManager to use for resolving namespaces for prefixes in the XPath expression.

Returns

The first XmlNode that matches the XPath query or null if no matching node is found. The XmlNode should not be expected to be connected "live" to the XML document. That is, changes that appear in the XML document may not appear in the XmlNode, and vice versa.

Remarks

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:

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 a node selected. For more information, see Select Nodes Using XPath Navigation.

For example, if you had the following XML:

Example

 <bookstore xmlns="http://www.lucernepublishing.com">
  <book>
    <title>Pride And Prejudice</title>
  </book>
 </bookstore>

The following C# code selects the first book node:

Example

 XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);
 nsmgr.AddNamespace("ab", "http://www.lucernepublishing.com");
 XmlNode book = doc.SelectSingleNode("//ab:book", nsmgr);

Note:

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:

Example

 <bookstore xmlns="http://www.lucernepublishing.com">
   <book>
     <title>&apos;Emma&apos;</title>
   </book>
 </bookstore>

The following Visual Basic code selects an element that contains single quotes:

Example

 Dim nsmgr As XmlNamespaceManager = New XmlNamespaceManager(doc.NameTable)
 nsmgr.AddNamespace("ab", "http://www.lucernepublishing.com")
 book = root.SelectSingleNode("descendant::ab:book[ab:title=""'Emma'""]", nsmgr)

This method is a Microsoft extension to the Document Object Model (DOM).

Requirements

Namespace: System.Xml
Assembly: System.Xml (in System.Xml.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0