C# と VB.NET の質問掲示板

以下のような方法はあります。デシリアライズも問題ないです。
https://stackoverflow.com/questions/7385921/how-to-write-a-comment-to-an-xml-file-when-using-the-xmlserializer

対象クラスに余計なパブリックメンバを定義することになるので、あまりシンプルではないですが・・・


using System;
using System.Windows.Forms;
using System.Reflection;
using System.Xml;
using System.Xml.Serialization;
using System.Runtime.CompilerServices;

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            var fileName = @"test.xml";
            var obj = new SampleClass() { Number = 123, Message = "メッセージ1"};
            XmlSerializer serializer = new XmlSerializer(typeof(SampleClass));
            
            using(var sw = new System.IO.StreamWriter(fileName, false, new System.Text.UTF8Encoding(false)))
            {
                serializer.Serialize(sw, obj);
            }
        }
    }

    public class SampleClass
    {

        public int Number { get; set; }


        [XmlAnyElement("MessageXmlComment")]
        public XmlComment MessageXmlComment { get { return GetType().GetXmlComment(); } set { } }

        [XmlComment("Messageのコメント")]
        public string Message { get; set; }

    }

    [AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
    public class XmlCommentAttribute : Attribute
    {
        public XmlCommentAttribute(string value)
        {
            this.Value = value;
        }

        public string Value { get; set; }
    }

    public static class XmlCommentExtensions
    {
        const string XmlCommentPropertyPostfix = "XmlComment";

        static XmlCommentAttribute GetXmlCommentAttribute(this Type type, string memberName)
        {
            var member = type.GetProperty(memberName);
            if (member == null)
                return null;
            var attr = member.GetCustomAttribute<XmlCommentAttribute>();
            return attr;
        }

        public static XmlComment GetXmlComment(this Type type, [CallerMemberName] string memberName = "")
        {
            var attr = GetXmlCommentAttribute(type, memberName);
            if (attr == null)
            {
                if (memberName.EndsWith(XmlCommentPropertyPostfix))
                    attr = GetXmlCommentAttribute(
                        type, memberName.Substring(0, memberName.Length - XmlCommentPropertyPostfix.Length)
                        );
            }
            if (attr == null || string.IsNullOrEmpty(attr.Value))
                return null;
            return new XmlDocument().CreateComment(attr.Value);
        }
    }
}