如何序列化属性上的属性或跳过类层次结构

Question

我有一个类，我正在使用XmlSerializer序列化。 除了其他属性，我还需要在对象中添加一块预先构建的xml。 我已经在这篇文章中询问了如何处理xml的问题： 如何在序列化对象时删除手动添加的xml字符串的空命名空间属性？

现在我需要为包含xml字符串的属性添加一个属性。 我理解如何将属性添加到类而不是属性。 如果我创建一个新类来保存属性，我会在输出中获得额外的层次结构。

这是我的简化代码：

public class Book
{
    public string Title { get; set; }

    public string Author { get; set; }

    public XmlElement Extension { get; set; }

    public Book()
    {
    }

    public void AddExtension()
    {
        string xmlString = "<AdditionalInfo xmlns=\"http://www.somenamespace.com\">" +
                                "<SpecialHandling>Some Value</SpecialHandling>" +
                           "</AdditionalInfo>";

        this.Extension = GetElement(xmlString);
    }

    public static XmlElement GetElement(string xml)
    {
        XmlDocument doc = new XmlDocument();

        doc.LoadXml(xml);

        return doc.DocumentElement;
    }
}

static void Main(string[] args)
{
    TestSerialization p = new TestSerialization();

    Book bookOne = new Book();

    bookOne.Title = "How to Fix Code";
    bookOne.Author = "Dee Bugger";

    bookOne.AddExtension();

    System.Xml.Serialization.XmlSerializer serializer = new XmlSerializer(typeof(Book), "http://www.somenamespace.com");

    using (var writer = new StreamWriter("C:\\BookReport.xml"))
    using (var xmlWriter = XmlWriter.Create(writer, new XmlWriterSettings { Indent = true }))
    {
        serializer.Serialize(xmlWriter, bookOne);
    }
}

它生成以下输出：

<?xml version="1.0" encoding="utf-8"?>
<Book xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://www.somenamespace.com">
  <Title>How to Fix Code</Title>
  <Author>Dee Bugger</Author>
  <Extension>
    <AdditionalInfo xmlns="http://www.somenamespace.com">
      <SpecialHandling>Some Value</SpecialHandling>
    </AdditionalInfo>
  </Extension>
</Book>

现在我需要向Extension添加一个属性，使Extension输出看起来像：

...
<Extension Modifier="ABC">
    <AdditionalInfo xmlns="http://www.somenamespace.com">
      <SpecialHandling>Some Value</SpecialHandling>
    </AdditionalInfo>
</Extension>

有没有办法改变Book类来做到这一点？ 我试图创建一个Extension类来保存Modifier属性和xml字符串的XmlElement，但这导致了一个额外的级别：

public class Extension
{
    [XmlAttribute]
    public string Modifier { get; set; }

    [XmlElementAttribute("Extension")]
    public XmlElement ExtensionAsElement { get; set; }

    public Extension()
    {
    }

    public Extension(XmlElement extensionAsElement)
    {
        this.Modifier = "ABC";

        this.ExtensionAsElement = extensionAsElement;
    }
}

public class Book
{
    public string Title { get; set; }

    public string Author { get; set; }

    [XmlElementAttribute("Extension")]
    public Extension ExtensionObj { get; set; }

    public Book()
    {
    }

    public void AddExtension()
    {
        string xmlString = "<AdditionalInfo xmlns=\"http://www.somenamespace.com\">" +
                                "<SpecialHandling>Some Value</SpecialHandling>" +
                           "</AdditionalInfo>";

        this.ExtensionObj = new Extension(GetElement(xmlString));
    }

    public static XmlElement GetElement(string xml)
    {
        XmlDocument doc = new XmlDocument();

        doc.LoadXml(xml);

        return doc.DocumentElement;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<Book xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://www.somenamespace.com">
  <Title>How to Fix Code</Title>
  <Author>Dee Bugger</Author>
  <Extension Modifier="ABC">
    <Extension>
      <AdditionalInfo xmlns="http://www.somenamespace.com">
        <SpecialHandling>Some Value</SpecialHandling>
      </AdditionalInfo>
    </Extension>
  </Extension>
</Book>

注意：这是我的代码的一个过于简化的示例，Book类不是我的根。 我只需要序列化，而不是反序列化。

Answer 1

您可以使用[XmlAnyElement("Extension")]指定您的Extension属性应该按原样插入XML流作为元素<Extension>本身，而不是作为该名称元素的子元素。 完成后，您将能够使用SetAttribute()和GetAttribute()在元素本身上设置属性。

因此，您的Book类变为：

public class Book
{
    public string Title { get; set; }

    public string Author { get; set; }

    [XmlAnyElement("Extension")]
    public XmlElement Extension { get; set; }

    public Book()
    {
        this.Extension = new XmlDocument().CreateElement("Extension");
    }

    public Book AddExtension()
    {
        string innerXmlString = "<AdditionalInfo xmlns=\"http://www.somenamespace.com\">" +
                                "<SpecialHandling>Some Value</SpecialHandling>" +
                           "</AdditionalInfo>";
        if (Extension == null)
            // Since Extension is marked with [XmlAnyElement("Extension")], its value must
            // be an XmlElement named "Extension".  Its InnerXml can be anything.
            Extension = new XmlDocument().CreateElement("Extension");
        Extension.InnerXml = innerXmlString;
        return this;
    }

    const string ModifierName = "Modifier";

    [XmlIgnore]
    public string Modifier
    {
        get
        {
            if (Extension == null)
                return null;
            return Extension.GetAttribute(ModifierName);
        }
        set
        {
            if (Extension == null)
                AddExtension();
            if (value == null)
                Extension.RemoveAttribute(ModifierName);
            else
                Extension.SetAttribute(ModifierName, value);
        }
    }
}

并从以下创建XML：

var bookOne = new Book { Title = "How to Fix Code", Author = "Dee Bugger", Modifier = "AAA" }
    .AddExtension();

产生结果：

 <Book xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <Title>How to Fix Code</Title> <Author>Dee Bugger</Author> <Extension Modifier="AAA"> <AdditionalInfo xmlns="http://www.somenamespace.com"> <SpecialHandling>Some Value</SpecialHandling> </AdditionalInfo> </Extension> </Book>