using System;

using System.Text.RegularExpressions;

public class Program

{

        private static readonly string _htmlSpanTo = "<span class=\"taio-renraku-to me-2\">To</span>";

        private static readonly string _htmlImageTo = "<img class=\"{0}\" src=\"/{1}\">";

        private static readonly string _htmlNoImageTo = "<span class=\"{0} profile-img-inline\"><i class=\"icofont-user-alt-7 {1}\"></i></span>";

        private static readonly string _htmlSpanName = "<span class=\"fw-bold\">{0}</span>";

        public static readonly string CommentTo = "[To:{0}]";

        public static readonly string CommentToAll = "[toAll]";

    public static void Main()

    {

        var pattern = new Regex(@"\[To:(\S+)\](.+\sさん)");

            var replaceString = pattern.Replace(

                "[To:8001]testap1 さん \n[To:2]西尾次郎 さん", new MatchEvaluator((Match match) => {

                    var profileImage = "abc";

​

                    var image = "def";

​

                    return $"{_htmlSpanTo} " +

                                    $"{image}" +

                                    $"{string.Format(_htmlSpanName, match.Groups[2].Value)}";

                }));

            replaceString = replaceString.Replace("[toAll]", $"{_htmlSpanTo} " +

                $"{string.Format(_htmlSpanName, "All")}");

        Console.WriteLine(replaceString);

    }

}