请参阅下面的代码，该代码将 XML 写入包含 3 个对象列表的简单类文件。列表中的 3 个对象彼此递减，Base、Derived1、Derived2。我在序列化期间使用 XMLArrayItemAttributes 覆盖名称。这在 .NET 3.0 中运行良好，但现在在 .NET 4.0 中输出不同的结果。请参阅下面的输出，特别注意第二个后代项目 DerivedItem2。
有没有人对此有任何经验，以及我如何修复它以在 .NET 4.0 中像在 v3.5 中那样工作？
似乎我无法控制数组项被覆盖的顺序。它似乎不是将它们添加到 XMLArrayItems 的顺序。
编辑：我刚刚尝试了使用 MONO 对框架版本 4.0 和 4.5 的相同示例，它适用于那些。这可能只是 Microsoft 框架版本的错误吗？
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Collections;
using System.Xml.Serialization;
using System.Xml;
using System.Xml.Schema;
using System.IO;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
TestGroup g = new TestGroup();
XmlSerializer s = new XmlSerializer(typeof(TestGroup), g.GetOverrides());
TextWriter w = new StreamWriter("c:\\#\\test.xml");
s.Serialize(w, g);
w.Close();
}
}
public class TestGroup
{
public List<BaseItem> Items { get; set; }
public TestGroup()
{
Items = new List<BaseItem>();
BaseItem b = new BaseItem();
b.BaseName = "Base Name";
Items.Add(b);
DerivedItem d1 = new DerivedItem();
d1.BaseName = "D1";
d1.DerivedName = "D1";
Items.Add(d1);
DerivedItem2 d2 = new DerivedItem2();
d2.BaseName = "D2";
//d2.DerivedName = "D2";
d2.Derived2Name = "D2";
Items.Add(d2);
}
public XmlAttributeOverrides GetOverrides()
{
XmlAttributes atts = new XmlAttributes();
for (int i = 0; i < Items.Count; i++)
{
BaseItem b = Items[i];
Type ItemType = b.GetType();
XmlArrayItemAttribute ItemAtt = new XmlArrayItemAttribute();
ItemAtt.ElementName = ItemType.Name;
ItemAtt.Type = ItemType;
atts.XmlArrayItems.Add(ItemAtt);
}
XmlAttributeOverrides attOvers = new XmlAttributeOverrides();
attOvers.Add(typeof(TestGroup), "Items", atts);
return attOvers;
}
}
public class BaseItem : IXmlSerializable
{
public string BaseName;
public XmlSchema GetSchema()
{
return null;
}
public void ReadXml(XmlReader reader)
{
// not required for example
}
public virtual void WriteXml(XmlWriter writer)
{
writer.WriteElementString("BaseName", this.BaseName);
}
}
public class DerivedItem: BaseItem
{
public string DerivedName;
public override void WriteXml(XmlWriter writer)
{
base.WriteXml(writer);
writer.WriteElementString("DerivedName", this.DerivedName);
}
}
public class DerivedItem2: DerivedItem
{
public string Derived2Name;
public override void WriteXml(XmlWriter writer)
{
base.WriteXml(writer);
writer.WriteElementString("Derived2Name", this.Derived2Name);
}
}
输出原件（.NET 3.0）：
<?xml version="1.0" encoding="utf-8"?>
<TestGroup xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Items>
<BaseItem>
<BaseName>Base Name</BaseName>
</BaseItem>
<DerivedItem>
<BaseName>D1</BaseName>
<DerivedName>D1</DerivedName>
</DerivedItem>
<DerivedItem2>
<BaseName>D2</BaseName>
<DerivedName />
<Derived2Name>D2</Derived2Name>
</DerivedItem2>
</Items>
</TestGroup>
输出更改（.NET 4.0）：
<?xml version="1.0" encoding="utf-8"?>
<TestGroup xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Items>
<BaseItem>
<BaseName>Base Name</BaseName>
</BaseItem>
<DerivedItem>
<BaseName>D1</BaseName>
<DerivedName>D1</DerivedName>
</DerivedItem>
<DerivedItem>
<BaseName>D2</BaseName>
<DerivedName />
<Derived2Name>D2</Derived2Name>
</DerivedItem>
</Items>
</TestGroup>
更新：.NET 4.5 的输出
<?xml version="1.0" encoding="utf-8"?>
<TestGroup xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Items>
<BaseItem>
<BaseName>Base Name</BaseName>
</BaseItem>
<BaseItem>
<BaseName>D1</BaseName>
<DerivedName>D1</DerivedName>
</BaseItem>
<DerivedItem2>
<BaseName>D2</BaseName>
<DerivedName />
<Derived2Name>D2</Derived2Name>
</DerivedItem2>
</Items>
</TestGroup>
更新：打开 app.config 中的调试开关如下，引用自http://msdn.microsoft.com/en-us/library/aa302290.aspx，我发现序列化应用覆盖的顺序是与我填充覆盖数组的顺序不同。有谁知道这个顺序是如何确定或覆盖的？
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<system.diagnostics>
<switches>
<add name="XmlSerialization.Compilation" value="4" />
</switches>
</system.diagnostics>
</configuration>
这给了我 ac# 输出文件，显示覆盖顺序不正确：
void Write2_TestGroup(string n, string ns, global::WindowsFormsApplication1.TestGroup o, bool isNullable, bool needType) {
if ((object)o == null) {
if (isNullable) WriteNullTagLiteral(n, ns);
return;
}
if (!needType) {
System.Type t = o.GetType();
if (t == typeof(global::WindowsFormsApplication1.TestGroup)) {
}
else {
throw CreateUnknownTypeException(o);
}
}
WriteStartElement(n, ns, o, false, null);
if (needType) WriteXsiType(@"TestGroup", @"");
{
global::System.Collections.Generic.List<global::WindowsFormsApplication1.BaseItem> a = (global::System.Collections.Generic.List<global::WindowsFormsApplication1.BaseItem>)((global::System.Collections.Generic.List<global::WindowsFormsApplication1.BaseItem>)o.@Items);
if (a != null){
WriteStartElement(@"Items", @"", null, false);
for (int ia = 0; ia < ((System.Collections.ICollection)a).Count; ia++) {
global::WindowsFormsApplication1.BaseItem ai = (global::WindowsFormsApplication1.BaseItem)a[ia];
if ((object)(ai) != null){
if (ai is global::WindowsFormsApplication1.DerivedItem) {
WriteSerializable((System.Xml.Serialization.IXmlSerializable)((global::WindowsFormsApplication1.DerivedItem)ai), @"DerivedItem", @"", true, true);
}
else if (ai is global::WindowsFormsApplication1.BaseItem) {
WriteSerializable((System.Xml.Serialization.IXmlSerializable)((global::WindowsFormsApplication1.BaseItem)ai), @"BaseItem", @"", true, true);
}
else if (ai is global::WindowsFormsApplication1.DerivedItem2) {
WriteSerializable((System.Xml.Serialization.IXmlSerializable)((global::WindowsFormsApplication1.DerivedItem2)ai), @"DerivedItem2", @"", true, true);
}
else if ((object)(ai) != null){
throw CreateUnknownTypeException(ai);
}
}
}
WriteEndElement();
}
}
WriteEndElement(o);
}