using System;

using System.Collections.Generic;

using System.Linq;

using System.Xml.Linq;

public class Program

{

    public static void Main()

    {

        List<string> list = new List<string> { "A", "B", "C" };

        List<string> list2 = new List<string> { "1", "2", "3" };

​

        XDocument xDocument = 

            new XDocument(new XDeclaration("1.0", "UTF-8", "yes"),

                          new XElement("SENDREQUEST",

                                       new XElement("ADID", "UID"),

                                       new XElement("APPLICATIONID", new XAttribute("Type","AN"), "申請案號"),

                                       new XElement("PROSPECTID", "代碼"),

                                       new XElement("SENDTO", list.Select(m => new XElement("TO", m))),

                                       new XElement("SENDFILE", list2.Select(n => new XElement("FILENAME", n))),

                                       new XElement("DATA1", "Subject"),

                                       new XElement("DATA2", "Body")

                                      ));

        string xml = xDocument.ToString();

        Console.WriteLine(xml);

    }

}