如何在不使用包装元素的情况下对多态数组进行XML序列化

Question

想要将我的数据序列化为以下格式：

<?xml version="1.0" encoding="ibm850"?>
<Batch Name="Test batch">
   <ExecuteCommand Command="..." />
   <WaitCommand Seconds="5" />
</Batch>

但是我得到的是这个（请注意包装“Commands”元素）

<?xml version="1.0" encoding="ibm850"?>
<Batch Name="Test batch">
  <Commands><!-- I want to get rid of thiw wrapper Commands element and just  -->
    <ExecuteCommand Command="..." />
    <WaitCommand Seconds="5" />
  </Commands>
</Batch>

以下是用于生成此代码示例的样本代码：

public class BaseCommand //base class
{
    [XmlAttribute]
    public string Result { get; set; }
}

public class ExecuteCommand : BaseCommand
{
    [XmlAttribute]
    public string Command { get; set; }
}

public class WaitCommand : BaseCommand
{
    [XmlAttribute]
    public int Seconds { get; set; }
}

public class Batch
{
    [XmlAttribute]
    public string Name { get; set; }

    private List<BaseCommand> _commands = new List<BaseCommand>();
    [XmlArrayItem(typeof(ExecuteCommand))]
    [XmlArrayItem(typeof(WaitCommand))]
    public List<BaseCommand> Commands
    {
        get
        {
            return _commands;
        }
        set
        {
            _commands = value;
        }
    }

    public static void Main()
    {
        XmlSerializer serializer = new XmlSerializer(typeof(Batch));

        Batch b = new Batch();
        b.Name = "Test batch";
        b.Commands.Add(new ExecuteCommand() { Command = "..." });
        b.Commands.Add(new WaitCommand() { Seconds = 5 });

        serializer.Serialize(Console.Out, b);
        Console.Read();
    }
}

我在这个主题上搜索并阅读了大量文章。它们似乎都提供了针对单个类类型（未使用继承）的序列化集合的解决方案。我使用继承，但似乎没有什么作用。不幸的是，由于遗留支持，我必须输出精确的XML文档。

- kaalen

Answer 1

这是很久以前的事了，但最终我自己解决了问题。

解决方法是为每个支持的派生类型添加[XmlElement]属性到集合属性中。

private List<BaseCommand> _commands = new List<BaseCommand>();
[XmlElement(typeof(ExecuteCommand))]
[XmlElement(typeof(WaitCommand))]
public List<BaseCommand> Commands
{
    get
    {
        return _commands;
    }
    set
    {
        _commands = value;
    }
}

- kaalen