Get the XPath to an XElement?
https://stackoverflow.com/questions/451950
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I've got an XElement deep within a document. Given the XElement (and XDocument?), is there an extension method to get its full (i.e. absolute, e.g. /root/item/element/child) XPath?
E.g. myXElement.GetXPath()?
EDIT: Okay, looks like I overlooked something very important. Whoops! The index of the element needs to be taken into account. See my last answer for the proposed corrected solution.
Solution
The extensions methods:
public static class XExtensions
{
/// <summary>
/// Get the absolute XPath to a given XElement
/// (e.g. "/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 sample 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 settle this. No?
OTHER TIPS
I updated the code by Chris to take into account namespace prefixes. Only the GetAbsoluteXPath method is modified.
public static class XExtensions
{
/// <summary>
/// Get the absolute XPath to a given XElement, including the namespace.
/// (e.g. "/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.");
}
}
Let me share my latest modification to this class. Basicaly it excludes index if element has no sibling and includes namespaces with local-name() operator has i was having issues with the namespace prefix.
public static class XExtensions
{
/// <summary>
/// Get the absolute XPath to a given XElement, including the namespace.
/// (e.g. "/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.");
}
}
This is actually a duplicate of this question. While it's not marked as the answer, the method in my answer to that question is the only way of unambiguously formulating the XPath to a node within an XML document that will always work under all circumstances. (It also works for all node types, not just elements.)
As you can see, the XPath it produces is ugly and abstract. but it addresses the concerns that many answerers have raised here. Most of the suggestions made here produce an XPath that, when used to search the original document, will produce a set of one or more nodes that includes the target node. It's that "or more" that's the problem. For instance, if I have an XML representation of a DataSet, the naive XPath to a specific DataRow's element, /DataSet1/DataTable1, also returns the elements of all of the other DataRows in the DataTable. You can't disambiguate that without knowing something about how the XML is forumlated (like, is there a primary-key element?).
But /node()[1]/node()[4]/node()[11], there's only one node that it'll ever return, no matter what.
As part of a different project I developed an extension method to generate a simple XPath to an element. It is similar to the selected answer, but supports XAttribute, XText, XCData and XComment in addition to XElement. It's available as code nuget, project page here: xmlspecificationcompare.codeplex.com
If you're looking for something natively provided by .NET the answer is no. You would have to write your own extension method to do this.
There can be several xpaths that lead to the same element, so finding the simplest xpath that leads to the node is not trivial.
That said, it is quite easy to find an xpath to the node. Just step up the node tree until you read the root node and combine the node names and you have a valid xpath.
By "full xpath" I assume you mean a simple chain of tags since the number of xpaths which could potentially match any element could be very large.
The problem here is that it's very hard if not specifically impossible to build any given xpath which will reversibly trace back to the same element - is that a condition?
If "no" then perhaps you could build a query by recursively looping with reference to the current elements parentNode. If "yes", then you're going to be looking at extending that by cross referencing for index position within sibling sets, referecing ID-like attributes if they exist, and this is going to be very dependant on your XSD if a general solution is possible.
Microsoft has provided an extension method to do this since .NET Framework 3.5:
http://msdn.microsoft.com/en-us/library/bb156083(v=vs.100).aspx
Just add a using to System.Xml.XPath and invoke the following methods:
XPathSelectElement: select a single ElementXPathSelectElements: select elements and return as anIEnumerable<XElement>XPathEvaluate: select nodes (not only elements, but also text, comments etc.) and return as anIEnumerable<object>
