测试源代码如下，使用 VS2013 编写。
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using System; using System.Collections; using System.Collections.Generic; using System.Xml.Serialization; using System.IO; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { var f = new XmlSerializer(typeof(TestClass), new[] { typeof(DerivedClass1), typeof(ChildNS.DerivedClass1) }); var ns = new XmlSerializerNamespaces(); ns.Add("ns", "http://yourcompany.org/schemas/ns"); ns.Add("nsc", "http://yourcompany.org/schemas/ns/child"); ns.Add("xsi", "http://www.w3.org/2001/XMLSchema-instance"); using (var sw = new StringWriter()) { f.Serialize(sw, new TestClass(), ns); Console.WriteLine(sw.ToString()); } } } public class TestClass { public BaseClass BaseTest = new BaseClass(); public BaseClass BaseTest1 = new DerivedClass1(); [XmlElement(Namespace = "http://yourcompany.org/schemas/ns/child")] public BaseClass BaseTest2 = new ChildNS.DerivedClass1(); public BaseClass[] BaseArray1 = {new BaseClass(), new DerivedClass1()}; [XmlArrayItem(typeof(BaseClass), IsNullable = true), XmlArrayItem(typeof(DerivedClass1), IsNullable = true), XmlArrayItem(typeof(DerivedClass2), IsNullable = true)] public BaseClass[] BaseArray2 = { new BaseClass(), new DerivedClass1(), null, new DerivedClass2() }; [XmlArrayItem(typeof(BaseClass), IsNullable = true)] public BaseClass[] BaseArray3 = { new BaseClass(), new DerivedClass1(), null, new DerivedClass2() }; [XmlArrayItem(typeof(BaseClass))] public List<BaseClass> BaseList = new List<BaseClass> { new BaseClass(), new DerivedClass1() }; [XmlElement(IsNullable = true)] public object NullObject1 = null; public object NullObject2 = null; //public IEnumerable BaseListEnumerable = new List<BaseClass> { new BaseClass(), new DerivedClass1() }; } public class BaseClass { [XmlAttribute("value1", Namespace = "http://yourcompany.org/schemas/ns")] public int Value1; [XmlAttribute("value2")] public int Value2; [XmlAttribute("value3", Namespace = "http://yourcompany.org/schemas/ns")] public int Value3; } public class DerivedClass1 : BaseClass { [XmlAttribute("value4", Namespace = "http://yourcompany.org/schemas/ns")] public int Value4; } public class DerivedClass2 : BaseClass { [XmlAttribute("value4", Namespace = "http://yourcompany.org/schemas/ns")] public int Value4; } namespace ChildNS { //为类型强制指定 XML 名称，以及命名空间，以避免命名冲突。 [XmlType("ChildDerivedClass", Namespace = "http://yourcompany.org/schemas/ns/child")] public class DerivedClass1 : BaseClass { public int Value5; } } } |
运行结果如下
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<?xml version="1.0" encoding="utf-16"?> <TestClass xmlns:ns="http://yourcompany.org/schemas/ns" xmlns:nsc="http://yourcompany.org/schemas/ns/child" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <BaseTest ns:value1="0" value2="0" ns:value3="0" /> <BaseTest1 xsi:type="DerivedClass1" ns:value1="0" value2="0" ns:value3="0" ns:value4="0" /> <nsc:BaseTest2 xsi:type="nsc:ChildDerivedClass" ns:value1="0" value2="0" ns:value3="0"> <nsc:Value5>0</nsc:Value5> </nsc:BaseTest2> <BaseArray1> <BaseClass ns:value1="0" value2="0" ns:value3="0" /> <BaseClass xsi:type="DerivedClass1" ns:value1="0" value2="0" ns:value3="0" ns:value4="0" /> </BaseArray1> <BaseArray2> <BaseClass ns:value1="0" value2="0" ns:value3="0" /> <DerivedClass1 ns:value1="0" value2="0" ns:value3="0" ns:value4="0" /> <DerivedClass2 ns:value1="0" value2="0" ns:value3="0" ns:value4="0" /> </BaseArray2> <BaseArray3> <BaseClass ns:value1="0" value2="0" ns:value3="0" /> <BaseClass xsi:type="DerivedClass1" ns:value1="0" value2="0" ns:value3="0" ns:value4="0" /> <BaseClass xsi:nil="true" /> <BaseClass xsi:type="DerivedClass2" ns:value1="0" value2="0" ns:value3="0" ns:value4="0" /> </BaseArray3> <BaseList> <BaseClass ns:value1="0" value2="0" ns:value3="0" /> <BaseClass xsi:type="DerivedClass1" ns:value1="0" value2="0" ns:value3="0" ns:value4="0" /> </BaseList> <NullObject1 xsi:nil="true" /> </TestClass> |
可以看出，
- 在
XmlArrayItem(Attribute)、XmlElement等相关特性中指定 IsNullable = true 可以使得当前为 null / Nothing 的元素在序列化时产生一个包含 xsi:nil="true" 特性的 XML 元素。 - 在特性中指定元素的命名空间时，应当指定命名空间的 URI，尽管可以稍后在
XmlSerializerNamespaces中为这些 URI 指定对应的命名空间前缀。 - 需要序列化派生类时，总是 需要通过 XmlInclude 特性，或者通过
XmlSerializer的构造函数显式声明序列化过程中可能用到的派生类。 - 数组的序列化：可以通过
XmlArrayItem特性声明数组中可能包含的派生类类型。这些类型在序列化时会使用与之对应的元素名。如果存在未在XmlArrayItem中声明的派生类，而其基类在XmlArrayItem中声明过，则会使用基类对应的元素名，外加xsi:type特性声明实际派生类的类型。（关于这一点，可以参阅另一篇文章：MSDN中“（使用 XmlArrayItemAttribute 限定）序列化派生类”一节中的示例可能与实际有出入） - 我该滚去修改以前的代码了。