Returns a new XmlReader instance that can be used to read the current node, and all its descendants.
Assemblies: System.Xml (in System.Xml.dll)
System.Xml.ReaderWriter (in System.Xml.ReaderWriter.dll)
The XML reader isn't positioned on an element when this method is called.
An XmlReader method was called before a previous asynchronous operation finished. In this case, InvalidOperationException is thrown with the message “An asynchronous operation is already in progress.”
can be called only on element nodes. When the entire sub-tree has been read, calls to the Read method returns false. When the new XML reader has been closed, the original reader is positioned on the EndElement node of the sub-tree. Thus, if you called the method on the start tag of the book element, after the sub-tree has been read and the new XML reader has been closed, the original XML reader is positioned on the end tag of the book element.
You should not perform any operations on the original reader until the new reader has been closed. This action is not supported and can result in unpredictable behavior.
The method isn't intended for creating copies of the XML data that you can work with independently. It's designed to create a boundary around an XML element. This is useful if you want to pass data to another component for processing and you wish to limit how much of your data the component can access. When you pass an XML reader returned by the method to another application, the application can access only that XML element, not the entire XML document.
The following example shows how to use the method.
Dim settings As New XmlReaderSettings() settings.IgnoreWhitespace = True Using reader As XmlReader = XmlReader.Create("books.xml", settings) ' Position the reader on the second book node. reader.ReadToFollowing("Book") reader.Skip() ' Create another reader that contains just the second book node. Dim inner As XmlReader = reader.ReadSubtree() inner.ReadToDescendant("Title") Console.WriteLine(inner.Name) ' Do additional processing on the inner reader. After you ' are done, call Close on the inner reader and ' continue processing using the original reader. inner.Close() End Using
Use the following XML data to run the examples in this topic:
<?xml version="1.0" encoding="utf-8" ?> <Books> <Book> <Title>A Brief History of Time</Title> </Book> <Book> <Title>Principle Of Relativity</Title> </Book> <Book> <Title>Victory of Reason</Title> </Book> <Book> <Title>The Unicorn that did not Fail</Title> </Book> <Book> <Title>Rational Ontology</Title> </Book> <Book> <Title>The Meaning of Pizza</Title> </Book> </Books>
.NET FrameworkSupported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0
.NET Framework Client ProfileSupported in: 4, 3.5 SP1
Portable Class LibrarySupported in: Portable Class Library
.NET for Windows Store appsSupported in: Windows 8
Supported in: Windows Phone 8.1
Supported in: Windows Phone Silverlight 8.1
Supported in: Windows Phone Silverlight 8
Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)