使用LINQ to XML的XDocument保存XML时自闭合标签加空格是否正常？

1. 这是正常行为 #

XML规范明确允许自闭合标签的两种写法：<genre/>和<genre />，两种格式均合法，所有标准XML解析器都能正确识别处理，不会影响XML的功能与兼容性。

2. 空格出现的原因 #

这是.NET中XDocument内置的XML序列化规则。早期部分旧版XML解析器对无空格的自闭合标签存在兼容性问题，微软为最大化兼容性，默认在输出自闭合标签时会在斜杠前添加一个空格。

3. 为什么SaveOptions.DisableFormatting无效 #

SaveOptions.DisableFormatting仅用于关闭XML的缩进、换行等格式化调整，不会改变自闭合标签的基础序列化格式。无论是否启用格式化，XDocument都会按照默认规则输出带空格的自闭合标签。

4. 如何去掉空格（若有需求） #

如果业务场景要求必须使用无空格的自闭合标签，可通过以下两种方式处理：

• 方式一：字符串替换（简单快捷）
  先将XDocument转换为字符串，再替换掉自闭合标签中的空格：

  string pathFile = Server.MapPath("\\xmlFolder\\test.xml");
  XDocument xmldoc = XDocument.Load(pathFile);
  // 转换为字符串并替换格式
  string xmlContent = xmldoc.ToString();
  xmlContent = xmlContent.Replace(" />", "/>");
  // 写入文件
  File.WriteAllText(pathFile, xmlContent, Encoding.UTF8);
  

  注意：需确保XML内容中没有其他包含" />"的文本（比如属性值），避免误替换。

• 方式二：自定义XmlWriter（更严谨）
  继承XmlWriter并重写相关方法，自定义自闭合标签的输出格式，适合复杂场景，避免字符串替换的潜在风险：

  public class NoSpaceXmlWriter : XmlWriter
  {
      private readonly XmlWriter _innerWriter;
  
      public NoSpaceXmlWriter(XmlWriter innerWriter)
      {
          _innerWriter = innerWriter;
      }
  
      public override void WriteSelfClosingElement(string prefix, string localName, string ns)
      {
          // 自定义输出无空格的自闭合标签
          _innerWriter.WriteStartElement(prefix, localName, ns);
          _innerWriter.WriteEndElement();
      }
  
      // 其他抽象方法直接委托给_innerWriter实现
      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 void WriteString(string text) => _innerWriter.WriteString(text);
      public override void WriteSurrogateCharEntity(char lowChar, char highChar) => _innerWriter.WriteSurrogateCharEntity(lowChar, highChar);
      public override void WriteWhitespace(string ws) => _innerWriter.WriteWhitespace(ws);
      public override XmlWriterSettings Settings => _innerWriter.Settings;
      public override WriteState WriteState => _innerWriter.WriteState;
      public override void Close() => _innerWriter.Close();
  }
  

  使用示例：

  string pathFile = Server.MapPath("\\xmlFolder\\test.xml");
  XDocument xmldoc = XDocument.Load(pathFile);
  XmlWriterSettings settings = new XmlWriterSettings
  {
      Indent = true,
      Encoding = Encoding.UTF8
  };
  using (var innerWriter = XmlWriter.Create(pathFile, settings))
  using (var writer = new NoSpaceXmlWriter(innerWriter))
  {
      xmldoc.WriteTo(writer);
  }
  

内容的提问来源于stack exchange，提问作者Luke