如何强制XDocument在声明行中输出"UTF-8"？

using System;
using System.Xml;
using System.Xml.Linq;

class Program
{
    static void Main()
    {
        XDocument doc = new XDocument(
            new XDeclaration("1.0", "UTF-8", "yes"),
            new XElement("Root",
                new XElement("Child", "Hello World")
            )
        );

        XmlWriterSettings settings = new XmlWriterSettings();
        settings.Encoding = System.Text.Encoding.UTF8; // 设置编码为UTF-8

        using (XmlWriter writer = XmlWriter.Create(Console.Out, settings))
        {
            doc.Save(writer);
        }
    }
}