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();

        }

    }

​