On a recent project, I had to provide export functionality for a web grid’s data source that contained wildly varying data structures. The XML structure contained anywhere between 1 to 10 levels of nesting and we needed to be able to export this data into an Excel or comma separate values file.
This code will show you how to turn a complex XML tree structure into a list of key-value pairs.
For example, here is a relatively simple data structure:
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<Customer> <Name>John Smith</Name> <Address>123 Main St</Address> <City>Baltimore</City> <Phones> <Phone>4105551234</Phone> <Phone>4151134443</Phone> </Phones> <Contacts> <Contact> <Name>Jiminy Cricket</Name> <Title>CricketMaster</Title> </Contact> <Contact> <Name>Hans Solo</Name> <Title>Smuggler</Title> </Contact> </Contacts> </Customer> |
In order to get the structure ready for data export, this code turns the XML into a list of key value pairs.
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using System; using System.Collections.Generic; using System.Globalization; using System.Xml; using System.Xml.XPath; using System.Xml.Linq; namespace Neuroticode.Examples { ///<remarks> /// 2016-04-20 - Matt Cullinan /// </remarks> /// <summary> /// Takes an XmlNode and "flattens" it out to a dictionary format. Exporting to Excel is a common use case for this. /// </summary> public class XmlFlattener { private char _delim = '/'; private readonly bool _showZeroIndexIdentifier; private readonly XmlDocument _xmlDocument; private readonly XmlNamespaceManager _namespaceManager; private readonly List<KeyValuePair<string, string>> _flattenedXMLDoc; /// <summary> /// /// </summary> /// <param name="showZeroIndexIdentifier">If TRUE, elements that are first of their kind in the XML tree structure will be appended with a "0".</param> /// <param name="xmlDocument">The document to parse</param> public XmlFlattener(bool showZeroIndexIdentifier, XmlDocument xmlDocument) { _showZeroIndexIdentifier = showZeroIndexIdentifier; _xmlDocument = xmlDocument; _flattenedXMLDoc = new List<KeyValuePair<string, string>>(); _namespaceManager = new XmlNamespaceManager(xmlDocument.NameTable); } public List<KeyValuePair<string, string>> FlattenedXMLDoc { get { return _flattenedXMLDoc; } } ///<remarks> /// 2016-04-20 - Matt Cullinan - Created /// </remarks> /// <summary> /// Performs the flattening of the data. /// </summary> public void Flatten() { var namespaceDictionary = XmlNamespaceRetriever.GetNamespacedictionary(_xmlDocument, XmlNamespaceScope.All); loadNamespacesIntoManager(namespaceDictionary); flattenNode(_xmlDocument, string.Empty); } ///<remarks> /// 2016-04-22 - Matt Cullinan - Created /// </remarks> /// <summary> /// Adds namespace references to the instance namespace manager. /// </summary> /// <param name="namespaceDictionary"></param> private void loadNamespacesIntoManager(IDictionary<string, string> namespaceDictionary) { foreach (var namespaceKey in namespaceDictionary.Keys) { _namespaceManager.AddNamespace(namespaceKey, namespaceDictionary[namespaceKey]); } } private void flattenNode(XmlNode targetNode, string key) { while (targetNode != null) { //If top level node, continue to next node. if (targetNode.NodeType == XmlNodeType.Document) { targetNode = targetNode.FirstChild; key = string.Empty; continue; } switch (targetNode.NodeType) { case XmlNodeType.Element: var selfAndSiblings = targetNode.SelectNodes("../" + targetNode.Name, this._namespaceManager); //loop through collection until the node found is the current node (to store "index" information) for (var i = 0; i < selfAndSiblings.Count; i++) { if (targetNode == selfAndSiblings[i]) { moveKeyDeepOneLevel(ref key, targetNode, i); //If FirstChild is null, this element has blank value. Add to list and get the next node. if (targetNode.FirstChild == null) { _flattenedXMLDoc.Add(new KeyValuePair<string, string>(key, targetNode.InnerText)); targetNode = getNextNode(targetNode, ref key); } else { targetNode = targetNode.FirstChild; } flattenNode(targetNode, key); //break control flow because we've already attained our break; } } break; case XmlNodeType.Text: //Add to the list of key value pairs. _flattenedXMLDoc.Add(new KeyValuePair<string, string>(key, targetNode.InnerText)); //current target node is text. Get the parent of this node to begin traversing back up the XML tree. targetNode = getNextNode(targetNode.ParentNode, ref key); continue; default: throw new ArgumentException( string.Format( "The target node type must be of NodeType.Element or NodeType.Text. The type is {0}", targetNode.NodeType)); } break; } } private void moveKeyUpOneLevel(ref string key) { if (!string.IsNullOrEmpty(key)) key = key.Substring(0, key.LastIndexOf(_delim.ToString(CultureInfo.InvariantCulture), StringComparison.InvariantCulture)); } private void moveKeyDeepOneLevel(ref string key, XmlNode targetNode, int index) { key = key + _delim + targetNode.Name + (!_showZeroIndexIdentifier && index == 0 ? string.Empty : Convert.ToString(index)); } private XmlNode getNextNode(XmlNode node, ref string key) { if (node == null) return null; moveKeyUpOneLevel(ref key); if (node.NextSibling != null) { return node.NextSibling; } return getNextNode(node.ParentNode, ref key); } } ///<remarks> /// 2016-04-22 - Matt Cullinan /// </remarks> /// <summary> /// Returns all XML namespaces in an XML Document /// </summary> public class XmlNamespaceRetriever { public static IDictionary<string, string> GetNamespacedictionary(XmlDocument xmlDocument, XmlNamespaceScope xmlNamespaceScope) { var namespaceRetrievalDocument = XDocument.Parse(xmlDocument.InnerXml); var namespaceRetrievalNavigator = namespaceRetrievalDocument.CreateNavigator(); namespaceRetrievalNavigator.MoveToFollowing(XPathNodeType.Element); var namespaceDictionary = namespaceRetrievalNavigator.GetNamespacesInScope(xmlNamespaceScope); return namespaceDictionary; } } } |
And the console app…
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using System; using System.Xml; namespace Neuroticode.Examples { class Program { static void Main(string[] args) { var xmlDoc = new XmlDocument(); xmlDoc.LoadXml("<Customer> <Name>John Smith</Name> <Address>123 Main St</Address> <City>Baltimore</City> <Phones> <Phone>4105551234</Phone> <Phone>4151134443</Phone> </Phones> <Contacts> <Contact> <Name>Jiminy Cricket</Name> <Title>CricketMaster</Title> </Contact> <Contact> <Name>Hans Solo</Name> <Title>Smuggler</Title> </Contact> </Contacts></Customer>"); var flattener = new XmlFlattener(false, xmlDoc); flattener.Flatten(); foreach(var item in flattener.FlattenedXMLDoc) { Console.WriteLine(string.Format("Key: {0}, Value: {1}", item.Key, item.Value)); } Console.ReadLine(); } } } |
Here is the output:
