请参阅下面的代码,该代码将XML写出,以归档一个包含3个对象的列表的简单类。列表中的3个对象彼此降序,即Base,Derived1,Derived2。我使用XMLArrayItemAttributes覆盖序列化过程中的名称。在.NET 3.0中,此方法工作正常,但现在在.NET 4.0中输出不同的结果。请参见下面的输出,特别注意第二个后代项目DerivedItem2。

有没有人对此有任何经验,以及我如何将其像在v3.5中一样在.NET 4.0中修复?

看来我无法控制覆盖数组项的顺序。这似乎不是将它们添加到XMLArrayItems中的顺序。

编辑:我刚刚针对框架版本4.0和4.5使用MONO尝试了相同的示例,并且可以很好地使用它们。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);
    }
}

输出原始(.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>

输出已更改(.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:
如下所示打开app.config中的调试开关(从http://msdn.microsoft.com/en-us/library/aa302290.aspx引用),我发现序列化应用替代的顺序与填充替代数组的顺序不同。任何人都知道如何确定或覆盖此顺序吗?
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <system.diagnostics>
        <switches>
            <add name="XmlSerialization.Compilation" value="4" />
        </switches>
    </system.diagnostics>
</configuration>

这给了我一个C#输出文件,该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);
}

最佳答案

帕特

在.Net4中测试您的代码时,我设法重现了相同的问题,而不是更改为.Net4.5。

在.Net4.5中,输出似乎与您为.Net3引用的输出相同

因此,只需跳过.Net4即可,而只需使用.Net4.5

产生此问题的原因是由于如何在框架的内存中构造对象。
在.net4中,它们可能是从“基础”到“派生”的;在.Net3和.Net4.5中,它们是从“派生”到“基础”的(我认为更正确)。
更具体地讲,我相信:

.Net4框架将对象实例存储为基本类型,并带有指向派生实例的指针。

.Net4.5/.Net3框架将对象实例存储为派生类型,并带有指向基本实例的指针。

在这两种情况下,在常规情况下使用对象时,最终都会得到相同的结果。

我确实记得读过垃圾收集对.net4.5进行了一些改进,我相信这只是MS开发人员为优化性能而进行的更改的一部分。

在两个测试中,我都使用相同版本的XML Serializer(4.0)

07-28 08:45