// SO: https://stackoverflow.com/questions/66394287/group-group-c-sharp-class-properties-into-xmlelement-attributes-during-serializa/

using System;

using System.Xml;

using System.Xml.Serialization;

using System.IO;

public class Program

{

    public static void Main()

    {

        string xml = @"<SomeClass>

                            <Element1 attribute1=""1"" attribute2=""2"" />

                            <Element2 attribute1=""3"" attribute2=""4"" attribute3=""5"" attribute4=""6"" />

                        </SomeClass>";

        XmlSerializer serializer;

        SomeClass myClass;

        // deserialize

        using (StringReader sr = new StringReader(xml)) 

        {

            serializer = new XmlSerializer(typeof(SomeClass));

            myClass = (SomeClass)serializer.Deserialize(sr);

        }

        myClass.Dump();

        xml = "";

        // serialize

        using (var stringWriter = new StringWriter())

        using (var writer = XmlWriter.Create(stringWriter))

        {

            serializer.Serialize(writer, myClass);

            xml = stringWriter.ToString();

        }

        Console.WriteLine(xml);

    }

}

​

public class SomeClass 

{

    public Element1 Element1 { get; set; }

    public Element2 Element2 { get; set; }

}

​

public class Element1 

{

    [XmlAttribute]

    public int attribute1 { get; set; }

​

    [XmlAttribute]

    public int attribute2 { get; set; }

}

​

public class Element2

{

    [XmlAttribute]

    public int attribute1 { get; set; }

​

    [XmlAttribute]

    public int attribute2 { get; set; }

    [XmlAttribute]

    public int attribute3 { get; set; }

​

    [XmlAttribute]

    public int attribute4 { get; set; }

}