如何构建 xml 部分并保存到文件（本身不是有效的 xml 文档）

Question

我正在尝试构建 XML 文档的一部分，以包含在最终文档中。 使用XDocument时出现异常：

“此操作将创建结构不正确的文档。”

因为我的片段有多个“根”节点。

由于文件要包含在更大的文档中，我的基本元素不会出现在最终文档的根目录中。

XDocument constsDocument = new XDocument(
    new XComment($" Consts section generated on {DateTime.Now} "),
    new XComment($" First group of constants. "),
    FirstTextConsts(MyFirstCollection),
    new XComment($" Refrigerant constants. "),
    SecondTextConsts(MySecondCollection)
    );
// To avoid xml file starting with <?xml version="1.0" encoding="utf-8"?> use stringbuilder and StreamWriter.
StringBuilder sb = new StringBuilder();
XmlWriterSettings xws = new XmlWriterSettings
{
    OmitXmlDeclaration = true,
    Indent = true
};
using (XmlWriter xw = XmlWriter.Create(sb, xws))
{
    constsDocument.Save(xw);
}
System.IO.StreamWriter file = new System.IO.StreamWriter(_outputFileName);
file.WriteLine(sb.ToString()); 
file.Close();

编辑 1： 在创建文档时调用的两个方法（原则上）：

private static IEnumerable<XElement> FirstTextConsts(IEnumerable<MyClass> collection)
{
    return collection.Select(r => new XElement("const", 
            new XAttribute("name", $"IDENTIFIER_{r.Id}"),
            new XAttribute("translatable", "false"),
            new XElement("text",
                new XAttribute("lang","en"), r.Name)));            
}

private static IEnumerable<XElement> SecondTextConsts(IEnumerable<MyClass> collection)
{
    foreach (var obj in collection)
    {
        if (obj.SomeSelector)
            yield return new XElement("const", 
                new XAttribute("name", $"IDENTIFIER_{r.Id}"),
                new XAttribute("translatable", "false"),
                new XElement("text",
                    new XAttribute("lang","en"), r.Name)));            
        if (obj.SomeOtherSelector)
            yield return new XElement("const", 
                new XAttribute("name", $"IDENTIFIER_{r.Id}"),
                new XAttribute("translatable", "true")
                );            
    }
}

编辑 2： 由于我确实需要 XDocument 的灵活性来构建一个多级 xml 文档和辅助方法返回不同级别的 IEnumerable，因此我决定添加一个虚假元素并在写入文件之前再次将其删除：

XDocument constsDocument = new XDocument(
    new XElement("root", 
        new XComment($" Consts section generated on {DateTime.Now} "),
        new XComment($" First group of constants. "),
        FirstTextConsts(MyFirstCollection),
        new XComment($" Refrigerant constants. "),
        SecondTextConsts(MySecondCollection)
        )
    );

在写入文件之前，我会剥离元素：

    file.WriteLine(sb.ToString().Replace("<root>" + Environment.NewLine, "").Replace(Environment.NewLine + "</root>", ""));

Answer 1

您无法创建无效的XDocument（由于多个“根”节点）。因此，您需要创建一个节点列表，并将其写入文档片段。

var constsDocument = new List<XNode> {
           new XComment($" Consts section generated on {DateTime.Now} "),
           new XComment($" First group of constants. "),
           new XElement("example"),
           new XComment($" Refrigerant constants. "),
           new XElement("another")
};
// To avoid xml file starting with <?xml version="1.0" encoding="utf-8"?> use stringbuilder and StreamWriter.
StringBuilder sb = new StringBuilder();
XmlWriterSettings xws = new XmlWriterSettings
{
    OmitXmlDeclaration = true,
    Indent = true,
    ConformanceLevel = ConformanceLevel.Fragment
};
using (XmlWriter xw = XmlWriter.Create(sb, xws))
{
    foreach (var element in constsDocument)
    {
        element.WriteTo(xw);
    }
}
System.IO.StreamWriter file = new System.IO.StreamWriter(_outputPath);
file.WriteLine(sb.ToString());
file.Close();

---

编辑：要使用在 List 的对象初始化程序中返回 IEnumerable<XElement> 的方法，您必须稍微更改定义以及添加其他项的方式：

var constsDocument = new List<IEnumerable<XNode>> {
    new [] { new XComment($" Consts section generated on {DateTime.Now} ") },
    new [] { new XComment($" First group of constants. ") },
    FirstTextConsts(MyFirstCollection),
    new [] { new XComment($" Refrigerant constants. ") },
    SecondTextConsts(MySecondCollection)
);

...

foreach (var element in constsDocument.SelectMany(n => n))

Answer 2

您可以声明您希望 XML 只是一个片段并从 XDocument 切换到 XMLDocument：

XmlDocument constDocument = new XmlDocument();
constDocument.CreateComment(" Consts section generated on {DateTime.Now} ");
constDocument.CreateComment(" First group of constants. ");
FirstTextConsts(MyFirstCollection); // Need to be adapted
constDocument.CreateComment(" Refrigerant constants. ");
SecondTextConsts(MySecondCollection); // Need to be adapted
XmlDocumentFragment fragDocument = constDocument.CreateDocumentFragment();
fragDocument.InnerXml = "<const>fragment</const><const>fragment2</const>"; // Need to be adapted

StringBuilder sb = new StringBuilder();
XmlWriterSettings xws = new XmlWriterSettings
{
    ConformanceLevel = ConformanceLevel.Fragment,
    OmitXmlDeclaration = true,
    Indent = true
};
using (XmlWriter xw = XmlWriter.Create(sb, xws))
{
    fragDocument.WriteContentTo(xw);
}
System.IO.StreamWriter file = new System.IO.StreamWriter(_outputFileName);
file.WriteLine(sb.ToString()); 
file.Close();

或添加人工根元素：

"<aritificialroot>" + fragment + "</aritificialroot>"