using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Xml;

using System.IO;

using System.Diagnostics;

using System.Xml.Linq;

​

    public static class XmlPremOutHelper

    {

        public static void ReorderPremiumElements(TextReader from, TextWriter to)

        {

            var doc = XDocument.Load(from);

            foreach (var node in doc.Descendants("PREMout"))

            {

                var g = node.Elements().GroupBy(e => e.Name);

                foreach (var nodes in g)

                {

                    nodes.Remove();

                    node.Add(nodes);

                }

            }

            doc.Save(to);

        }

​

        public static void GroupPremiumElements(TextReader from, TextWriter to)

        {

            var doc = XDocument.Load(from);

            foreach (var node in doc.Descendants("PREMout"))

            {

                var lists = new[] { 

                    node.Elements("PremFromDate").ToList(),

                    node.Elements("PremToDate").ToList(),

                    node.Elements("AnnualPremium").ToList(),

                    node.Elements("ModePremium").ToList(),

                };

                if (!lists.Skip(1).All(l => l.Count == lists[0].Count))

                    throw new InvalidOperationException("Unequal list counts");

                foreach (var nodes in lists.ZipMany(l => l))

                {

                    nodes.Remove();

                    node.Add(new XElement("PREMoutData", nodes));

                }

            }

            doc.Save(to);

        }

    }

​

    public static class EnumerableExtensions

    {

        // Taken from

        // http://stackoverflow.com/questions/17976823/how-to-zip-or-rotate-a-variable-number-of-lists

        public static IEnumerable<TResult> ZipMany<TSource, TResult>(

            this IEnumerable<IEnumerable<TSource>> source,

            Func<IEnumerable<TSource>, TResult> selector)

        {

            // ToList is necessary to avoid deferred execution

            var enumerators = source.Select(seq => seq.GetEnumerator()).ToList();

            try

            {

                while (true)

                {

                    foreach (var e in enumerators)

                    {

                        bool b = e.MoveNext();

                        if (!b)

                            yield break;

                    }

                    // Again, ToList (or ToArray) is necessary to avoid deferred execution

                    yield return selector(enumerators.Select(e => e.Current).ToList());

                }

            }

            finally

            {

                foreach (var e in enumerators)

                    e.Dispose();

            }

        }

    }

​

    public class TestClass

    {

        public static string GetXml()

        {

            var xml = @"<xml>

<PREMout>

    <PolicyNumber>12345</PolicyNumber>

    <ModeCode>ANN</ModeCode>

    <PremFromDate>11/10/2015</PremFromDate>

    <PremToDate>12/12/2020</PremToDate>

    <AnnualPremium>400.00</AnnualPremium>

    <ModePremium>400.00</ModePremium>

    <PremFromDate>12/31/2020</PremFromDate>

    <PremToDate>12/12/2027</PremToDate>

    <AnnualPremium>5000.00</AnnualPremium>

    <ModePremium>5000.00</ModePremium>

</PREMout>

</xml>

";

            return xml;

        }

​

        public static void Test()

        {

            ConsoleAndDebug.WriteLine("Original XML: ");

            ConsoleAndDebug.WriteLine(XDocument.Parse(GetXml()));

​

            ConsoleAndDebug.WriteLine("Reordered XML:");

            Test(XmlPremOutHelper.ReorderPremiumElements);

​

            ConsoleAndDebug.WriteLine("Restructured XML:");

            Test(XmlPremOutHelper.GroupPremiumElements);

        }

​

​

​

        public static void Test(Action<TextReader, TextWriter> action)

        {

            var xmlString = GetXml();

            using (var reader = new StringReader(xmlString))

            using (var writer = new StringWriter())

            {

                action(reader, writer);

                ConsoleAndDebug.WriteLine(writer);

            }

        }

    }

​

    public static class ConsoleAndDebug

    {

        public static void WriteLine(object s)

        {

            Console.WriteLine(s);

            Debug.WriteLine(s);

        }

    }

​

    public class Program

    {

        public static void Main()

        {

            TestClass.Test();

        }

    }

​