Get XPath for XElement?

Question

I have an XElement deep inside the document. Given XElement (and XDocument?), Is there an extension method to get its full (i.e. absolute, e.g. /root/item/element/child ) XPath?

eg. myXElement.GetXPath ()?

EDIT: Well, it looks like I forgot something very important. Oops! You must consider the index of the element. See My last answer for a suggested fix.

Answer 1

Extension Methods:

 public static class XExtensions { /// <summary> /// Get the absolute XPath to a given XElement /// (eg "/people/person[6]/name[1]/last[1]"). /// </summary> public static string GetAbsoluteXPath(this XElement element) { if (element == null) { throw new ArgumentNullException("element"); } Func<XElement, string> relativeXPath = e => { int index = e.IndexPosition(); string name = e.Name.LocalName; // If the element is the root, no index is required return (index == -1) ? "/" + name : string.Format ( "/{0}[{1}]", name, index.ToString() ); }; var ancestors = from e in element.Ancestors() select relativeXPath(e); return string.Concat(ancestors.Reverse().ToArray()) + relativeXPath(element); } /// <summary> /// Get the index of the given XElement relative to its /// siblings with identical names. If the given element is /// the root, -1 is returned. /// </summary> /// <param name="element"> /// The element to get the index of. /// </param> public static int IndexPosition(this XElement element) { if (element == null) { throw new ArgumentNullException("element"); } if (element.Parent == null) { return -1; } int i = 1; // Indexes for nodes start at 1, not 0 foreach (var sibling in element.Parent.Elements(element.Name)) { if (sibling == element) { return i; } i++; } throw new InvalidOperationException ("element has been removed from its parent."); } } 

And the test:

 class Program { static void Main(string[] args) { Program.Process(XDocument.Load(@"C:\test.xml").Root); Console.Read(); } static void Process(XElement element) { if (!element.HasElements) { Console.WriteLine(element.GetAbsoluteXPath()); } else { foreach (XElement child in element.Elements()) { Process(child); } } } } 

And an example output:

 /tests/test[1]/date[1] /tests/test[1]/time[1]/start[1] /tests/test[1]/time[1]/end[1] /tests/test[1]/facility[1]/name[1] /tests/test[1]/facility[1]/website[1] /tests/test[1]/facility[1]/street[1] /tests/test[1]/facility[1]/state[1] /tests/test[1]/facility[1]/city[1] /tests/test[1]/facility[1]/zip[1] /tests/test[1]/facility[1]/phone[1] /tests/test[1]/info[1] /tests/test[2]/date[1] /tests/test[2]/time[1]/start[1] /tests/test[2]/time[1]/end[1] /tests/test[2]/facility[1]/name[1] /tests/test[2]/facility[1]/website[1] /tests/test[2]/facility[1]/street[1] /tests/test[2]/facility[1]/state[1] /tests/test[2]/facility[1]/city[1] /tests/test[2]/facility[1]/zip[1] /tests/test[2]/facility[1]/phone[1] /tests/test[2]/info[1] 

That should decide. No?

Answer 2

I updated the code by Chris to allow for namespace prefixes. Only the GetAbsoluteXPath method is changed.

 public static class XExtensions { /// <summary> /// Get the absolute XPath to a given XElement, including the namespace. /// (eg "/a:people/b:person[6]/c:name[1]/d:last[1]"). /// </summary> public static string GetAbsoluteXPath(this XElement element) { if (element == null) { throw new ArgumentNullException("element"); } Func<XElement, string> relativeXPath = e => { int index = e.IndexPosition(); var currentNamespace = e.Name.Namespace; string name; if (currentNamespace == null) { name = e.Name.LocalName; } else { string namespacePrefix = e.GetPrefixOfNamespace(currentNamespace); name = namespacePrefix + ":" + e.Name.LocalName; } // If the element is the root, no index is required return (index == -1) ? "/" + name : string.Format ( "/{0}[{1}]", name, index.ToString() ); }; var ancestors = from e in element.Ancestors() select relativeXPath(e); return string.Concat(ancestors.Reverse().ToArray()) + relativeXPath(element); } /// <summary> /// Get the index of the given XElement relative to its /// siblings with identical names. If the given element is /// the root, -1 is returned. /// </summary> /// <param name="element"> /// The element to get the index of. /// </param> public static int IndexPosition(this XElement element) { if (element == null) { throw new ArgumentNullException("element"); } if (element.Parent == null) { return -1; } int i = 1; // Indexes for nodes start at 1, not 0 foreach (var sibling in element.Parent.Elements(element.Name)) { if (sibling == element) { return i; } i++; } throw new InvalidOperationException ("element has been removed from its parent."); } } 

Answer 3

This is actually a duplicate of this question. Although this is not marked as an answer, the method my answer to this question is the only way to uniquely formulate XPath for a node in an XML document that will always work under any circumstances. (It also works for all types of node, not just for elements.)

As you can see, the XPath that it produces is ugly and abstract. but it addresses the problems that many defendants have raised. Most of the suggestions made here create XPath, which when used to search for a source document will create a set of one or more nodes that includes the target node. This is what “or more” is that problem. For example, if I have an XML representation of a DataSet, the naive XPath for a particular DataRow, /DataSet1/DataTable1 , also returns the elements of all other DataRows in the DataTable. You cannot fix this without knowing how the XML forum is (for example, is there a primary key element?).

But /node()[1]/node()[4]/node()[11] there is only one node that it will ever return, no matter what.

Answer 4

Let me share my latest modification with this class. This basically excludes the index, if the element does not have a sibling and includes namespaces with the local-name () operator, I am having problems with the namespace prefix.

 public static class XExtensions { /// <summary> /// Get the absolute XPath to a given XElement, including the namespace. /// (eg "/a:people/b:person[6]/c:name[1]/d:last[1]"). /// </summary> public static string GetAbsoluteXPath(this XElement element) { if (element == null) { throw new ArgumentNullException("element"); } Func<XElement, string> relativeXPath = e => { int index = e.IndexPosition(); var currentNamespace = e.Name.Namespace; string name; if (String.IsNullOrEmpty(currentNamespace.ToString())) { name = e.Name.LocalName; } else { name = "*[local-name()='" + e.Name.LocalName + "']"; //string namespacePrefix = e.GetPrefixOfNamespace(currentNamespace); //name = namespacePrefix + ":" + e.Name.LocalName; } // If the element is the root or has no sibling elements, no index is required return ((index == -1) || (index == -2)) ? "/" + name : string.Format ( "/{0}[{1}]", name, index.ToString() ); }; var ancestors = from e in element.Ancestors() select relativeXPath(e); return string.Concat(ancestors.Reverse().ToArray()) + relativeXPath(element); } /// <summary> /// Get the index of the given XElement relative to its /// siblings with identical names. If the given element is /// the root, -1 is returned or -2 if element has no sibling elements. /// </summary> /// <param name="element"> /// The element to get the index of. /// </param> public static int IndexPosition(this XElement element) { if (element == null) { throw new ArgumentNullException("element"); } if (element.Parent == null) { // Element is root return -1; } if (element.Parent.Elements(element.Name).Count() == 1) { // Element has no sibling elements return -2; } int i = 1; // Indexes for nodes start at 1, not 0 foreach (var sibling in element.Parent.Elements(element.Name)) { if (sibling == element) { return i; } i++; } throw new InvalidOperationException ("element has been removed from its parent."); } } 

Answer 5

In another project, I developed an extension method to create simple XPath for an element. It is similar to the selected answer, but supports XAttribute, XText, XCData and XComment in addition to XElement. It is available as code nuget , the project page is here: xmlspecificationcompare.codeplex.com

Answer 6

If you are looking for something originally provided by .NET, the answer is no. To do this, you will have to write your own extension method.

Answer 7

There may be several xpaths that lead to the same element, so finding the simplest xpath that leads to node is not trivial.

However, it is fairly easy to find the xpath for the node. Just raise the node tree until you see the root of the node, and join the node names, and you have a valid xpath.

Answer 8

By "full xpath" I assume that you mean a simple tag chain, since the number of xpaths that could potentially match any element can be very large.

The problem is that it is very difficult, if not specifically impossible, to build any given xpath that reversibly accesses the same element - is this a condition?

If not, perhaps you could build the query in a recursive loop with reference to the current parentNode elements. If yes, then you plan to expand this by cross-referencing the index position in sets of sister sites, referencing the identification attributes, if any, and it will be very dependent on your XSD if a common solution is possible.

Answer 9

Microsoft has provided an extension method for this, since the .NET Framework 3.5:

http://msdn.microsoft.com/en-us/library/bb156083 (v = vs .100) .aspx

Just add usage to System.Xml.XPath and call the following methods:

• XPathSelectElement : select one item
• XPathSelectElements : select the elements and return them as IEnumerable<XElement>
• XPathEvaluate : select the nodes (not only elements, but also text, comments, etc.) and return as IEnumerable<object>