StringWriter.ToString()破坏了xml C#

using System;
using System.IO;
using System.Xml;

public class Program
{
    public static void Main()
    {
        // 创建一个XmlWriter对象，将XML写入内存流中
        using (MemoryStream stream = new MemoryStream())
        {
            using (XmlWriter writer = XmlWriter.Create(stream))
            {
                // 在这里编写XML文档的结构
                writer.WriteStartDocument();
                writer.WriteStartElement("root");
                writer.WriteElementString("element", "value");
                writer.WriteEndElement();
                writer.WriteEndDocument();
            }

            // 将内存流转换为字符串
            string xmlString = System.Text.Encoding.UTF8.GetString(stream.ToArray());

            // 输出转换后的字符串
            Console.WriteLine(xmlString);
        }
    }
}