Applied XML Programming for Microsoft .NET.pdf - Csbdu.in

Console.WriteLine(nodeReader.Value);}}The while loop visits all the nodes belonging to the specified XML DOM subtree. Thenode reader class is initialized using the XmlNode object that is the root of the XMLDOM subtree.Updating Text and MarkupOnce an XML document is loaded in memory, you can enter all the needed changes bysimply accessing the property of interest and modifying the underlying value. Forexample, to change the value of an attribute, you proceed as follows:// Retrieve a particular node and update an attributeXmlNode n = root.SelectSingleNode("days");n.Attributes["module"] = 1;To insert many nodes at the same time and in the same parent, you can exploit a littletrick based on the concept of a document fragment. In essence, you concatenate all thenecessary markup into a string and then create a document fragment, as shown here:XmlDocumentFragment df = doc.CreateDocumentFragment();df.InnerXml = "ValueAnotherValue";parentNode.AppendChild(df);Set the InnerXml property of the document fragment node with the string, and then addthe newly created node to the parent. The nodes defined in the body of the fragmentwill be inserted one after the next.In general, when you set the InnerXml property on an XmlNode-based class, anydetected markup text will be parsed, and the new contents will replace the existingcontents. For this reason, if you want simply to add new children to a node, passthrough the XmlDocumentFragment class, as described in the previous paragraph, andavoid using InnerXml directly on the target node.Detecting ChangesCallers are notified of any changes that affect nodes through events. You can set eventhandlers at any time and even prior to loading the document, as shown here:XmlDocument doc = new XmlDocument();doc.NodeInserted += new XmlNodeChangedEventHandler(Changed);doc.Load(fileName);If you use the preceding code, you will get events for each insertion during the buildingof the XML DOM. The following code illustrates a minimal event handler:void Changed(object sender, XmlNodeChangedEventArgs e){Console.WriteLine(e.Action.ToString());}Note that by design XML DOM events give you a chance to intervene before and after anode is added, removed, or updated.187