如何在没有包装元素的情况下对多态数组进行XML序列化

Question

Want to serialise my data into this:

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

But instead I'm getting this (note the wrapping Commands element)

<?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>

Here's the sample code used to produce this:

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();
    }
}

I searched and read heaps of articles on this topic. They all seem to provide solution for serializing collections with a single class type (no inheritance used). I use inheritance and nothing seems to work. Unfortunately I have to output precise XML document due to legacy support

Answer 1

This was quite some time ago but I eventually figured it out on my own.

The solution was to add [XmlElement] attribute for each of the supported derived types to the collection property

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