using System;

using System.Collections.Generic;

using System.Text;

using System.Linq;

using System.Xml.Serialization;

using System.Xml;

using System.Xml.Linq;

using System.IO;

using System.Data;

using System.Runtime.Serialization;

using System.Runtime.Serialization.Formatters.Binary;

using System.IO.Compression;

using System.Reflection;

​

using NUnit.Framework; //NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/72620855/group-xdocument-by-multiple-nodes-dynamic?noredirect=1#comment128280597_72620855

​

    public static partial class XNodeExtensions

    {

        public static XElement CopyAndGroupChildrenByColumns(this XElement root, Func<XName, int, bool> columnFilter, XName groupName) =>

            new XElement(root.Name, 

                         root.Attributes(),

                         root.Elements()

                         .Select((row) => (row, key : row.Elements().Where((e, i) => columnFilter(e.Name, i)).Select(e => (e.Name, e.Value)).ToHashSet()))

                         .GroupByKeyAndSet(pair => pair.row.Name, pair => pair.key)

                         .Select(g => new XElement(g.Key.Key, 

                                                   g.Key.Set.Select(p => new XElement(p.Name, p.Value)).Concat(g.Select(i => new XElement(groupName, i.row.Elements().Where((e, i) => !columnFilter(e.Name, i))))))));

​

        public static IEnumerable<IGrouping<(TKey Key, HashSet<TItem> Set), TSource>> GroupByKeyAndSet<TSource, TKey, TItem>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, HashSet<TItem>> setSelector) =>

            Enumerable.GroupBy(source, (i) => (keySelector(i), setSelector(i)), new CombinedComparer<TKey, HashSet<TItem>>(null, HashSet<TItem>.CreateSetComparer()));

    }

​

    public class CombinedComparer<T1, T2> : IEqualityComparer<ValueTuple<T1, T2>>

    {

        readonly IEqualityComparer<T1> comparer1;

        readonly IEqualityComparer<T2> comparer2;

        public CombinedComparer(IEqualityComparer<T1> comparer1, IEqualityComparer<T2> comparer2) => (this.comparer1, this.comparer2) = (comparer1 ?? EqualityComparer<T1>.Default, comparer2 ?? EqualityComparer<T2>.Default);

        public bool Equals(ValueTuple<T1, T2> x, ValueTuple<T1, T2> y) => comparer1.Equals(x.Item1, y.Item1) && comparer2.Equals(x.Item2, y.Item2);

        public int GetHashCode(ValueTuple<T1, T2> obj) => HashCode.Combine(comparer1.GetHashCode(obj.Item1), comparer2.GetHashCode(obj.Item2));

    }

​

    public static partial class XNodeExtensions

    {

        public static XDocument ToXDocument(this DataTable dt, XmlWriteMode mode = XmlWriteMode.IgnoreSchema)

        {

            var doc = new XDocument();

            using (var writer = doc.CreateWriter())

                dt.WriteXml(writer, mode);

            return doc;

        }

    }

​

    public class TestClass

    {

        public static void Test()

        {

            Console.WriteLine("Testing grouping of DataTable XML:");

​

            TestDataTable(GetOriginalXml(), GetExpectedXml());

            Console.WriteLine("\nTesting grouping of XML with mixed row names:");

​

            var doc = XDocument.Parse(GetXml());

​

            var d1 = TestByIndex(doc);

            var d2 = TestByName(doc);

            Assert.That(XNode.DeepEquals(d1.Root, d2.Root));

        }

        public static void TestDataTable(string originalXml, string expectedXml)

        {

            var dt = GetDataTable(originalXml);

            var doc = dt.ToXDocument(XmlWriteMode.IgnoreSchema);

            // Group by the first four columns with all remaining elements collected under a <BID_INTERVALS> sequence of elements:

            XName groupName = doc.Root.Name.Namespace + "BID_INTERVALS";

            var grouped = doc.Root.CopyAndGroupChildrenByColumns((n, i) => (i < 4), groupName);

​

            var newDoc = new XDocument(grouped);

            Console.WriteLine(newDoc);

​

            var expectedXElement = XElement.Parse(expectedXml);

            Assert.That(XNode.DeepEquals(grouped, XElement.Parse(expectedXml)));

        } 

        public static XDocument TestByIndex(XDocument doc)

        {

            var ns = doc.Root.Name.Namespace;

            XName groupName = ns + "BID_INTERVALS";

​

            var newRoot = doc.Root.CopyAndGroupChildrenByColumns((n, i) => (i < 4), groupName);

            var newDoc = new XDocument(newRoot);

            Console.WriteLine(newDoc);

            return newDoc;

        }

​

        public static XDocument TestByName(XDocument doc)

        {

            var ns = doc.Root.Name.Namespace;

            XName groupName = ns + "BID_INTERVALS";

            HashSet<XName> names = new (new [] { ns + "Col1", ns + "Col2", ns + "Col3", ns + "Date" } );

​

            var newRoot = doc.Root.CopyAndGroupChildrenByColumns((n, i) => names.Contains(n), groupName);

​

            var newDoc = new XDocument(newRoot);

            Console.WriteLine(newDoc);

            return newDoc;

        }

        static DataTable GetDataTable(string originalXml)

        {

            var ds = new DataSet();

            using var reader = new StringReader(originalXml);

            ds.ReadXml(reader);

            var dt = ds.Tables[0];

            return dt;

        }

        static string GetOriginalXml() => @"<ROOT>

<ROW>

    <Col1>CESLP</Col1>

    <Col2>MRP</Col2>

    <Col3>372</Col3>

    <Date>20040101</Date>

        <SEGMENT>1</SEGMENT>

        <Price>10</Price>

        <QTY>5</QTY>

</ROW>

<ROW>

    <Col1>CESLP</Col1>

    <Col2>MRP</Col2>

    <Col3>372</Col3>

    <Date>20040101</Date>

        <SEGMENT>2</SEGMENT>

        <Price>15</Price>

        <QTY>6</QTY>

</ROW>

<ROW>

    <Col1>CESLP</Col1>

    <Col2>MRP</Col2>

    <Col3>372</Col3>

    <Date>20040102</Date>

        <SEGMENT>1</SEGMENT>

        <Price>11</Price>

        <QTY>5</QTY>

</ROW>

<ROW>

    <Col1>CESLP</Col1>

    <Col2>MRP</Col2>

    <Col3>372</Col3>

    <Date>20040102</Date>

        <SEGMENT>2</SEGMENT>

        <Price>14.5</Price>

        <QTY>6</QTY>

</ROW>

</ROOT>";

​

    static string GetExpectedXml() => @"<ROOT>

<ROW>

    <Col1>CESLP</Col1>

    <Col2>MRP</Col2>

    <Col3>372</Col3>

    <Date>20040101</Date>

    <BID_INTERVALS>

        <SEGMENT>1</SEGMENT>

        <Price>10</Price>

        <QTY>5</QTY>

    </BID_INTERVALS>

    <BID_INTERVALS>

        <SEGMENT>2</SEGMENT>

        <Price>15</Price>

        <QTY>6</QTY>

    </BID_INTERVALS>

</ROW>

<ROW>

    <Col1>CESLP</Col1>

    <Col2>MRP</Col2>

    <Col3>372</Col3>

    <Date>20040102</Date>

    <BID_INTERVALS>

        <SEGMENT>1</SEGMENT>

        <Price>11</Price>

        <QTY>5</QTY>

    </BID_INTERVALS>

    <BID_INTERVALS>

        <SEGMENT>2</SEGMENT>

        <Price>14.5</Price>

        <QTY>6</QTY>

    </BID_INTERVALS>

</ROW>

</ROOT>";

    static string GetXml() => @"<ROOT  xmlns=""defaultNameSpace"" foo=""bar"">

<ROW>

    <Col1>CESLP</Col1>

    <Col2>MRP</Col2>

    <Col3>372</Col3>

    <Date>20040101</Date>

        <SEGMENT>1</SEGMENT>

        <Price>10</Price>

        <QTY>5</QTY>

</ROW>

<ROW>

    <Col1>CESLP</Col1>

    <Col2>MRP</Col2>

    <Col3>372</Col3>

    <Date>20040101</Date>

        <SEGMENT>2</SEGMENT>

        <Price>15</Price>

        <QTY>6</QTY>

</ROW>

<ROW>

    <Col1>CESLP</Col1>

    <Col2>MRP</Col2>

    <Col3>372</Col3>

    <Date>20040102</Date>

        <SEGMENT>1</SEGMENT>

        <Price>11</Price>

        <QTY>5</QTY>

</ROW>

<ROW>

    <Col1>CESLP</Col1>

    <Col2>MRP</Col2>

    <Col3>372</Col3>

    <Date>20040102</Date>

        <SEGMENT>2</SEGMENT>

        <Price>14.5</Price>

        <QTY>6</QTY>

</ROW>

<FOO>

    <Col1>CESLP</Col1>

    <Col2>MRP</Col2>

    <Col3>372</Col3>

    <Date>20040102</Date>

        <SEGMENT>2</SEGMENT>

        <Price>15</Price>

        <QTY>6</QTY>

</FOO>

</ROOT>";

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1}, {2})", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , Environment.Version, Environment.OSVersion);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

                Console.WriteLine("Failed with unhandled exception: ");

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​