How To Use Xpath Syntax To Select XML Nodes

In this blog, you will learn how and when to use different syntaxes of XPath for selecting nodes using expression and steps.

In this blog, I am demonstrating different syntaxes of XPATH on selecting nodes using expression and steps.

 

I will be using this below XML file as a reference to my demo.

<?xml version="1.0" encoding="UTF-8"?>

<TrainingData>

  <Courses name=".net">
      <Training name="c# basic">
          <content name="data types" hours="1"></content>
          <content name="events and delegates" hours="2"></content>
      <price>100</price>
      </Training>
      <Training name=".net core">
          <content name="REST API" hours="2"></content>
          <content name="MVC" hours="2"></content>
      <price>200</price>
      </Training>
      <Training name="VB">
          <content name="data types" hours="1"></content>
      <price>50</price>
      </Training>
  </Courses>

  <Courses name="Javascript">
    <Training name="basics">
          <content name="data types" hours="1"></content>
      <price>100</price>
      </Training>
  </Courses>

  <Courses name="non technical">
    <Training name="negotiation skills">
      <price>60</price>
    </Training>
    <Training name="7 habits">
      <price>70</price>
    </Training>
  </Courses>

  <Others>
    <Training name="Time managment">
      <price>0</price>
    </Training>
  </Others>

</TrainingData>

Let's read the file first and get the XDocument object to use XPath syntax. 

static void Main(string[] args)
{
    var location = new Uri(Assembly.GetEntryAssembly().CodeBase).LocalPath;
    var path = Path.GetDirectoryName(location);
    var filePath = args.Any() ? args[0] : Path.Combine(path, "..you path of xml\\Trainingdata.xml");

    if (!File.Exists(filePath))
    {
        throw new InvalidOperationException();
    }

    var document = XDocument.Load(filePath);
}

Let's start with XPath syntax one by one to select nodes based on your requirement.

 

Selecting Nodes

 

Select all Courses and trainings nodes using '//' symbol for all elements.

//select all Courses Node irrespective of where it is defined.
document.XPathSelectElements("//Courses");

//select all training node irrespective of where it is defined.
document.XPathSelectElements("//Training");

Select root node course by using the '/' symbol.

var rootcourse = document.XPathSelectElement("TrainingData/Courses");

// select the current node by '.' symbol, here root as current node.
var selectingcurrent = rootcourse.XPathSelectElements("./Training[@name='c# basic']");

// select all tranings under .net course
var firstCourse = document.XPathSelectElement("//Courses[@name='.net']");
var alltrainings = firstCourse.XPathSelectElements("./Training");

Reading multiple elements

 

Select all others and non technical trainings use '//' for all elements and for union use '|' sysmbol.

document.XPathSelectElements("//Courses[@name = 'non technical'] | //Others");

Predicates (indexing, last(), @, *)

 

Select the first course (using the index or last() etc predicates).

document.XPathSelectElements("//Courses[1]");
 // same way can be done for last "//Courses[last()]"

Using @

// select all content node having hour attribute, @ symbol used for attribute.
var hourAttribite = document.XPathSelectElements("//content[@hours]");

// select all content node having hour=2 attribute.
var hour2Attribite = document.XPathSelectElements("//content[@hours = 2]");

Using node name direclty

// select all tranings whose price >= 100.
var trainingpricegreat100 = document.XPathSelectElements("//Training[price >= 100]");

Using *

// select all conent having name as datatype.
// use '*' to match any type of node where name is equal to data type
var hourAttribite = document.XPathSelectElements("//*[@name='data types']");
// OR
var allconenthaveDatatype = document.XPathSelectElements("//content[@name='data types']");

I hope you liked this blog. The code is attached with a performance test. Let me know any questions you might have in the comments section.

Thanks!