如何在C#应用中将CRLF统一保存为XML十进制实体
而非十六进制

问题根源 #

直接用Replace("\r\n", "
")无效，是因为XElement会自动转义字符串中的&符号，把
变成
，最终输出的不是预期的十进制实体。另外不同环境下XDocument.Save的换行编码差异，源于系统默认的换行处理逻辑不同。

解决方案 #

方法一：自定义XmlWriter处理换行实体 #

这是通用方案，不管XML结构复杂度如何，都能统一将\r\n替换为十进制实体：

1. 实现自定义XmlWriter

public class DecimalEntityXmlWriter : XmlWriter
{
    private readonly XmlWriter _innerWriter;

    public DecimalEntityXmlWriter(XmlWriter innerWriter)
    {
        _innerWriter = innerWriter;
    }

    public override void WriteString(string text)
    {
        // 将\r\n替换为十进制实体，其他字符正常输出
        string processedText = text.Replace("\r\n", "
");
        _innerWriter.WriteString(processedText);
    }

    // 以下方法直接委托给内部XmlWriter，无需修改
    public override void Close() => _innerWriter.Close();
    public override void Flush() => _innerWriter.Flush();
    public override string LookupPrefix(string ns) => _innerWriter.LookupPrefix(ns);
    public override void WriteBase64(byte[] buffer, int index, int count) => _innerWriter.WriteBase64(buffer, index, count);
    public override void WriteCData(string text) => _innerWriter.WriteCData(text);
    public override void WriteCharEntity(char ch) => _innerWriter.WriteCharEntity(ch);
    public override void WriteChars(char[] buffer, int index, int count) => _innerWriter.WriteChars(buffer, index, count);
    public override void WriteComment(string text) => _innerWriter.WriteComment(text);
    public override void WriteDocType(string name, string pubid, string sysid, string subset) => _innerWriter.WriteDocType(name, pubid, sysid, subset);
    public override void WriteEndAttribute() => _innerWriter.WriteEndAttribute();
    public override void WriteEndDocument() => _innerWriter.WriteEndDocument();
    public override void WriteEndElement() => _innerWriter.WriteEndElement();
    public override void WriteEntityRef(string name) => _innerWriter.WriteEntityRef(name);
    public override void WriteFullEndElement() => _innerWriter.WriteFullEndElement();
    public override void WriteProcessingInstruction(string name, string text) => _innerWriter.WriteProcessingInstruction(name, text);
    public override void WriteRaw(string data) => _innerWriter.WriteRaw(data);
    public override void WriteRaw(char[] buffer, int index, int count) => _innerWriter.WriteRaw(buffer, index, count);
    public override void WriteStartAttribute(string prefix, string localName, string ns) => _innerWriter.WriteStartAttribute(prefix, localName, ns);
    public override void WriteStartDocument(bool standalone) => _innerWriter.WriteStartDocument(standalone);
    public override void WriteStartDocument() => _innerWriter.WriteStartDocument();
    public override void WriteStartElement(string prefix, string localName, string ns) => _innerWriter.WriteStartElement(prefix, localName, ns);
    public override WriteState WriteState => _innerWriter.WriteState;
    public override void WriteSurrogateCharEntity(char lowChar, char highChar) => _innerWriter.WriteSurrogateCharEntity(lowChar, highChar);
    public override void WriteWhitespace(string ws) => _innerWriter.WriteWhitespace(ws);
}

2. 使用自定义XmlWriter保存XML

XElement xelm = *******; // 包含带\r\n的XML文本
XDocument xdoc = new XDocument(xelm);

var settings = new XmlWriterSettings
{
    Encoding = new UTF8Encoding(false),
    Indent = true // 根据需求决定是否格式化XML
};

using (var strWriter = new StreamWriter(path, false, settings.Encoding))
using (var xmlWriter = XmlWriter.Create(strWriter, settings))
using (var customWriter = new DecimalEntityXmlWriter(xmlWriter))
{
    xdoc.Save(customWriter);
}

方法二：手动写入原始实体内容（适用于简单XML结构） #

如果你的XML节点结构简单，没有复杂的子节点和属性，可以直接用XmlWriter.WriteRaw写入带实体的内容，避免自动转义：

XElement xelm = *******;
string processedText = xelm.Value.Replace("\r\n", "
");

using (var strWriter = new StreamWriter(path, false, new UTF8Encoding(false)))
using (var xmlWriter = XmlWriter.Create(strWriter))
{
    xmlWriter.WriteStartDocument();
    xmlWriter.WriteStartElement(xelm.Name.LocalName);
    // 写入原始实体内容，不触发转义
    xmlWriter.WriteRaw(processedText);
    xmlWriter.WriteEndElement();
    xmlWriter.WriteEndDocument();
}

关键说明 #

• NewLineHandling.None无法直接生成十进制实体，它只是禁止XmlWriter自动转换换行符，适合需要保留原始换行的场景，但不符合本次需求。
• 自定义XmlWriter的核心是重写WriteString方法，在输出文本前替换换行符为十进制实体，同时保留其他字符的正常处理逻辑。

内容的提问来源于stack exchange，提问作者Naveen