具有 IXmlSerializable 的命名空间前缀

Question

对要使用的正确装饰器或可能需要的任何设计有点困惑。当序列化一个实现 IXmlSerializable 的类时，有没有办法在 XmlRoot 元素中包含命名空间及其前缀？

例如类定义。

using System;
using System.Xml;
using System.Xml.Schema;
using System.Xml.Serialization;
[XmlRoot("Classy", Namespace = XML_NS)]
public class TestClass : IXmlSerializable
{
    private const string XML_PREFIX = ""; // default namespace
    private const string XML_NS = "www.123.com";
    private const string XML_MEMBER_PREFIX = "me";
    private const string XML_MEMBER_NS = "member.com";

    [XmlNamespaceDeclarations]
    public XmlSerializerNamespaces xmlsn {
        get {
            XmlSerializerNamespaces xsn = new XmlSerializerNamespaces();
            xsn.Add(XML_PREFIX, XML_NS);
            xsn.Add(XML_MEMBER_PREFIX, XML_MEMBER_NS);
            return xsn;
        }
    }

    void IXmlSerializable.WriteXml(XmlWriter writer) {
        writer.WriteElementString(XML_MEMBER_PREFIX, "Member1.5",
                                  XML_MEMBER_NS, Member1);
        writer.WriteElementString(XML_MEMBER_PREFIX, "Member2.5",
                                  XML_MEMBER_NS, Member2.ToString());
        writer.WriteElementString(XML_PREFIX, "Member3.5", XML_NS, Member3);
    }

    //[XmlElement(ElementName = "Member1.5", Namespace = XML_MEMBER_NS)]
    public string Member1 {
        get { return "init"; }
        set { ; }
    }
    //[XmlElement(ElementName = "Member2.5", Namespace = XML_MEMBER_NS)]
    public int Member2 {
        get { return 3; }
        set { ; }
    }
    //[XmlElement(ElementName = "Member3.5", Namespace = XML_NS)]
    public string Member3 {
        get { return "default namespace"; }
        set { ; }
    }

    // ignore ReadXml/GetSchema
    XmlSchema IXmlSerializable.GetSchema() { return null; }
    void IXmlSerializable.ReadXml(XmlReader reader) { return; }
}

当通过以下方式序列化时：

TestClass tc = new TestClass();
XmlSerializer ser = new XmlSerializer(typeof(TestClass)); 
ser(writer, tc, tc.xmlsn); // just a plain XmlWriter to Console.Out

输出是

<?xml version="1.0" encoding="utf-8"?>
<Classy xmlns="www.123.com">
    <me:Member1.5 xmlns:me="member.com">init</me:Member1.5>
    <me:Member2.5 xmlns:me="member.com">3</me:Member2.5>
    <Member3.5>default namespace</Member3.5>
</Classy>

我期待的输出是：

<?xml version="1.0" encoding="utf-8"?>
<Classy xmlns:me="member.com" xmlns="www.123.com">
    <me:Member1.5>init</me:Member1.5>
    <me:Member2.5>3</me:Member2.5>
    <Member3.5>default namespace</Member3.5>
</Classy>

第二个是 XmlSerializer 的输出，如果删除了类的 IXmlSerializable 实现并且取消注释 XmlElement 装饰器。我知道返回的两个 Xml 文档都是有效的，但最好尝试删除多余的命名空间声明。我认为这样的事情是可能的，因为 IXmlSerializable 旨在更好地控制您的类的序列化/反序列化方式。

更新： 一个非常有趣的答案建议修改 XmlWriterSettings！看起来这会通过修改 NamespaceHandling 属性来清除所有内容。但是，这仍然会导致为每个成员重写命名空间。完整序列化代码如下：

XmlSerializer ser = new XmlSerializer(typeof(TestClass));
TestClass tc = new TestClass();

XmlWriterSettings xmlSet = new XmlWriterSettings();
xmlSet.Encoding = System.Text.Encoding.UTF8;
xmlSet.Indent = true;
xmlSet.NamespaceHandling = NamespaceHandling.OmitDuplicates;
XmlWriter writer = XmlWriter.Create(Console.Out, xmlSet);

ser.Serialize(writer, tc); // with/without tc.xmlsn same result
writer.Flush();
writer.Close();

Answer 1

我只是在 WriteXml 中添加了一个字符串属性。成功了！

void IXmlSerializable.WriteXml(XmlWriter writer) {
        writer.WriteAttributeString("xmlns:me", "member.com");
        writer.WriteAttributeString("xmlns", "www.123.com");
        writer.WriteElementString(XML_MEMBER_PREFIX, "Member1.5",
                                  XML_MEMBER_NS, Member1);
        writer.WriteElementString(XML_MEMBER_PREFIX, "Member2.5",
                                  XML_MEMBER_NS, Member2.ToString());
        writer.WriteElementString(XML_PREFIX, "Member3.5", XML_NS, Member3);
    }

并从类中删除 [XmlRoot("Classy", Namespace = XML_NS)] 和 xmlsn 属性。

Answer 2

按照建议使用 WriteAttributeString 并不完全正确。以下是如何正确使用它的示例：

在 WriteXml 方法开头添加如下内容：

    public void WriteXml(System.Xml.XmlWriter writer)
    {
        writer.WriteAttributeString("xmlns", "xsi", null, "http://www.w3.org/2001/XMLSchema-instance");
        writer.WriteAttributeString("xmlns", "xsd", null, "http://www.w3.org/2001/XMLSchema");
}

Answer 3

您需要设置 XmlWriterSetting 才能使其工作。请见下文

http://msdn.microsoft.com/en-us/library/system.xml.xmlwritersettings.aspx