XML 序列化一个子 class

Question

I have a class:

public abstract class BaseClass
{

}

public class FirstChild:BaseClass
{

}

public class SecondChild:BaseClass
{

}

public class Request
{
public BaseClass Child {get;set;}

}

I have added serializable attribute on all of the classes and included XmlInclude on Baseclass, firstchild and secondchild classes.

I want to achieve this:
<Request>
   <FirstChild/>
</Request>

or

<Request>
   <SecondChild/>
</Request>

I create the request using:

Request request = new Request();
request.Child = new FirstChild();

And then serialize it.

but I keep getting this:

<Request  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">

<Type  xsi:type="FirstChild">
</Type>

</Request>

Can you please point what I am not doing right?

Answer 1

In order to do this you need to use the XmlArrayItem or XmlElement attributes. Also, if you want the sub-classed instance to be a sub-element of your Child element, it's easier if you treat the Child property as a BaseClass[] of length 1.

Thus your class will look like this:

public abstract class BaseClass
{

}

public class FirstChild:BaseClass
{

}

public class SecondChild:BaseClass
{

}

public class Request
{
        [XmlArrayItem(Type = typeof(FirstChild), ElementName = "FirstChild")]
        [XmlArrayItem(Type = typeof(SecondChild), ElementName = "SecondChild")] 
        public BaseClass[] Child {get;set;}

}

This will result in the XML you're looking for.

Answer 2

Can you try this code.. also i'm assuming your actual class has properties in them.

using (MemoryStream ms = new MemoryStream())
{
    XmlWriterSettings xrs = new XmlWriterSettings();
    xrs.Encoding = Encoding.UTF8;
    using (XmlWriter writer = XmlWriter.Create(ms, xrs))
    {
        XmlSerializer serializer = new XmlSerializer(obj.GetType());
        serializer.Serialize(writer, obj);

        writer.Flush();
    }

    using (StreamReader sr = new StreamReader(ms))
    {
        ms.Position = 0;
        xml = sr.ReadToEnd();
    }
}

Answer 3

I don't see any easy way to do this. I would create a helper class RequestMemento for this purpose:

using System;
using System.IO;
using System.Xml.Serialization;
using System.ComponentModel;

public abstract class BaseClass
{}

public class FirstChild:BaseClass
{}

public class SecondChild:BaseClass
{}

[XmlRoot("Request")]
[XmlType("Request")]
public class RequestMemento
{
    [DefaultValue(null)]
    public FirstChild First { get; set; }

    [DefaultValue(null)]
    public SecondChild Second { get; set; }

    [XmlIgnore]
    public BaseClass Child
    {
        get
        {
            return (BaseClass)First ?? (BaseClass)Second;
        }
        set
        {
            First = value as FirstChild;
            Second = value as SecondChild;
        }
    }
}

class App
{
    static void Main()
    {
        var memento = new RequestMemento();
        memento.Child = new FirstChild();

        XmlSerializer serializer = new XmlSerializer(typeof(RequestMemento));
        using (var writer = new StreamWriter("1.xml"))
        {
            serializer.Serialize(writer, memento);
        }
    }
}