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",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; }
}

通过以下序列化时：

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,但尝试删除冗余的命名空间声明会很好.我认为这样的事情是可能的,因为IXmlSerializable旨在更好地控制类的序列化/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名称空间.完整的序列化代码如下：

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();