questions/46774190/get-last-child-element-using-xmlreader

CSharp · Console

/Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Serialization;
using System.Xml;
using System.IO;
using System.Xml.Linq;
using System.Xml.Schema;
using System.Net;
using System.Xml.XPath;
using System.Globalization;
using System.Collections;


    // https://stackoverflow.com/questions/46774190/get-last-child-element-using-xmlreader

    public static class XmlReaderExtensions
    {
        public static IEnumerable<IEnumerable<XElement>> ReadNestedElements(this XmlReader xmlReader, string outerName, string innerName)
        {
            while (!xmlReader.EOF)
            {
                if (xmlReader.NodeType == System.Xml.XmlNodeType.Element && xmlReader.Name == outerName)
                {
                    using (var subReader = xmlReader.ReadSubtree())
                    {
                        yield return subReader.ReadElements(innerName);
                    }
                }
                xmlReader.Read();
            }
        }

        public static IEnumerable<XElement> ReadElements(this XmlReader xmlReader, string name)
        {
            while (!xmlReader.EOF)
            {
                if (xmlReader.NodeType == System.Xml.XmlNodeType.Element && xmlReader.Name == name)
                {
                    var element = (XElement)XNode.ReadFrom(xmlReader);
                    yield return element;
                }
                else
                {
                    xmlReader.Read();
                }
            }
        }
    }

    class TestClass
    {
        public static void Test()
        {
            Test(GetXml());
            Console.WriteLine("\nAll tests passed.");
        }

        public static void Test(string xmlString)
        {
            Console.WriteLine("\nTesting XML: ");
            Console.WriteLine(xmlString);
            Console.WriteLine();

            var indentedXml = XElement.Parse(xmlString).ToString(SaveOptions.None);
            var unindentedXml = XElement.Parse(xmlString).ToString(SaveOptions.None);

            var indentedValues = LastFieldValues(indentedXml);
            var unindentedValues = LastFieldValues(unindentedXml);

            Console.WriteLine("Indented last field values: ");
            Console.WriteLine(String.Join(",", indentedValues));

            Console.WriteLine("Unindented last field values: ");
            Console.WriteLine(String.Join(",", unindentedValues));

            // Parse the XML into an XDocument.
            // You can use use XDocument.Load(fileName) to load from a file
            var doc = XDocument.Parse(xmlString); 
            var xpathLastValues = doc
                .XPathSelectElements(@"//fields/field/value[last()]")
                .Select(e => e.Value)
                .ToList();

			Console.WriteLine("Last field values from XPathSelectElements(): ");
            Console.WriteLine(String.Join(",", xpathLastValues));
			
            Assert.IsTrue(indentedValues.SequenceEqual(unindentedValues));

            Assert.IsTrue(xpathLastValues.SequenceEqual(unindentedValues));
        }

        static List<string> LastFieldValues(string xml)
        {
            using (var textReader = new StringReader(xml))
            using (var xmlReader = XmlReader.Create(textReader))
            {
                return LastFieldValues(xmlReader);
            }
        }

        public static List<string> LastFieldValues(XmlReader reader)
        {
            var query = reader.ReadNestedElements("field", "value")
                .Select(l => l.LastOrDefault())
                .Where(v => v != null)
                .Select(v => (string)v);

            return query.ToList();
        }

        static string GetXml()
        {
            var xml = @"<fields>
        <field fieldid=""fdtElem3Group"">
          <value actionid=""1"" actiontype=""review"">123456789</value>
          <value actionid=""2"" actiontype=""review"">123456789</value>
          <value actionid=""3"" actiontype=""review"">123456789</value>
          <value actionid=""4"" actiontype=""review"">123456789</value>
          <value actionid=""5"" actiontype=""review"">123456789</value>
        </field>
        <field fieldid=""fdtElem7Group"">
          <value actionid=""1"" actiontype=""review"">29/10/75</value>
          <value actionid=""2"" actiontype=""review"">29/10/74</value>
          <value actionid=""3"" actiontype=""review"">29/10/74</value>
          <value actionid=""4"" actiontype=""review"">29/10/76</value>
          <value actionid=""5"" actiontype=""review"">29/10/74</value>
        </field>
        <field fieldid=""fdtElemNullGroup"" />
      </fields>";
            return xml;
        }
    }

    public class AssertionFailedException : System.Exception
    {
        public AssertionFailedException() : base() { }

        public AssertionFailedException(string s) : base(s) { }
    }

    public static class Assert
    {
        public static void IsTrue(bool value)
        {
            IsTrue(value, "failed");
        }

        public static void IsTrue(bool value, string message)
        {
            if (value == false)
                throw new AssertionFailedException(message ?? "failed");
        }
    }

						
	public class Program
	{
		public static void Main()
		{
			Console.WriteLine("Environment version: " + Environment.Version);
			Console.WriteLine();

			TestClass.Test();
		}
	}