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 NUnit.Framework; //NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/78090825/c-sharp-xmlserializer-output-multiple-xml-fragments-controlling-new-lines

​

#nullable enable

​

    public static partial class XmlExtensions

    {

        static Encoding Utf8EncodingNoBom { get; } = new UTF8Encoding(encoderShouldEmitUTF8Identifier: false);

        public static void SerializeFragmentsToXml<T>(this IEnumerable<T> enumerable, Stream stream, XmlSerializer? serializer = null, XmlSerializerNamespaces? ns = null)

        {

            var newLine = "\n";

            var newLineBytes = Utf8EncodingNoBom.GetBytes(newLine+newLine);

            var settings = new XmlWriterSettings()

            {

                NamespaceHandling = NamespaceHandling.Default,

                NewLineChars = newLine,

                Encoding = Utf8EncodingNoBom, // supress BOM

                Indent = true,

                NewLineHandling = NewLineHandling.Replace,

                OmitXmlDeclaration = true,

                WriteEndDocumentOnClose = false,

                CloseOutput = false, // Required to prevent the stream from being closed between items

                CheckCharacters = false,

                NewLineOnAttributes = false,

            };

            serializer ??= new XmlSerializer(typeof(T));

            ns ??= new XmlSerializerNamespaces(new[] { XmlQualifiedName.Empty });

​

            bool first = true;

            foreach (var item in enumerable)

            {

                if (!first)

                    stream.Write(newLineBytes);

                using (var xmlWriter = XmlWriter.Create(stream, settings))

                    serializer.Serialize(xmlWriter, item, ns);

                first = false;

            }

        }

    }

​

    // -----

​

    [System.Xml.Serialization.XmlTypeAttribute(TypeName = "flyingMonkey", Namespace = null)]

    public class FlyingMonkey

    {

        [System.Xml.Serialization.XmlAttributeAttribute()]

        public string name;

​

        public Limb[] limbs;

​

        public static FlyingMonkey Create(string? name = null) =>

            new FlyingMonkey()

            {

                name = name ?? "Koko",

                limbs = new Limb[]

                {

                    new Limb() { name = "leg" }, new Limb() { name = "arm" },

                    new Limb() { name = "tail" }, new Limb() { name = "wing" },

                }

            };

    }

​

    [System.Xml.Serialization.XmlTypeAttribute(TypeName = "limb", Namespace=null)]

    public class Limb

    {

        [System.Xml.Serialization.XmlAttributeAttribute()]

        public string name;

    }

​

​

    public class TestClass

    {

        public static void Test()

        {

            var items = new [] { "Koko", "POCO", "Loco" }.Select(n => FlyingMonkey.Create(n));

            using var stream = new MemoryStream(); // Replace with some FileStream when serializing to disk

            var serializer = new XmlSerializer(typeof(FlyingMonkey), defaultNamespace: null);

            items.SerializeFragmentsToXml(stream, serializer : serializer);

            var xml = Encoding.UTF8.GetString(stream.GetBuffer().AsSpan(0, (int)stream.Length));

​

            Console.WriteLine(xml);

        }

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1}, {2}, NewLine: {3}).", 

                              System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , Environment.Version, Environment.OSVersion,

                              System.Text.Json.JsonSerializer.Serialize(Environment.NewLine));

            //Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

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

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​