How to XML serialize a Generic List<T> containing multiple Types derived from a base class T

Question

I need to serialize to XML a datastructure based on Generics such as List<T>. The problem arises in that I want T to be a base class for multiple derived classes. When I try to serialize this I cannot get the derived classes to be serialized, only the base Class are serialized.

Eg;

[Serialize]
Class Node{
   private string n_info;
}

Class Node_A : Node {
   private string a_info;
}

Class node_B : Node {
  private string b_info;
}

List<Node> list = new List<Node>();
list.Add(new Node_A());
list.Add(new Node_B());

 XmlSerializer serializer = new XmlSerializer(typeof(List<Node>),
                    new Type[] { typeof(Node_A), typeof(Node_B) });

FileStream fstream = new FileStream("ListData.xml", FileMode.Create, FileAccess.Write, FileShare.None);
serializer.Serialize(fstream, list);
fstream.Close();

This runs but only serializes the Node Base Class attributes.

Answer 1

A bit late maybe, but...have you tried the XmlInclude attribute?
You need to set an XmlInclude entry on the base class for each subclass. In your example it would be:

...
[Serializable]
[XmlInclude(Node_A)]
[XmlInclude(Node_B)]
Class Node{
   private string n_info;
}
...

Ugly - yes, but there you go...

//Carl

Answer 2

Just a quick point but all your members are marked 'private' and you can only serialize public members with XmlSerializer.  Are you sure that this is not connected to your problem?

Answer 3

I got it working as follows..

 

// Create a sample List with test data

List<Node> list = new List<Node>();

list.Add(new AppNode("app1"));

list.Add(new DbNode("db1"));

 

// Serialise the list

XmlSerializer serializer = new XmlSerializer(typeof(List<Node>), new Type[] { typeof(AppNode), typeof(DbNode) });

FileStream fstream = new FileStream("List-Node.xml", FileMode.Create, FileAccess.Write, FileShare.None);

serializer.Serialize(fstream, list);

fstream.Close();

 

// Deserialise the list

fstream = new FileStream("List-Node.xml.xml", FileMode.Open, FileAccess.Read, FileShare.None);

list.Clear();

list = (List<Node>)serializer.Deserialize(fstream);

fstream.Close();

 

The Node, AppNode and DBNode are defined as follows:-

 

[Serializable]

public class Node

{

    public Node() {}    // Required for Serialization

 

    public Node(string nm)

    {

        Name = nm;

    }

 

    private string m_name = "";

    public string Name

    {

        get { return m_name; }

        set { m_name = value; }

     }

}

 

[Serializable]

public class AppNode : Node

{

     public AppNode() : base()  {  }     // Required for Serialization

 

     public AppNode(string nm) : base(nm)

     {

            AppInfo = "Some info about app";

     }

 

     private string m_appInfo;

     public string AppInfo

     {

         get { return m_appInfo; }

         set { m_appInfo = value; }

     }

}

 

[Serializable]

public class DbNode : Node

{   

    public DbNode() : base()    {}       // Required for Serialization

 

    public DbNode(string nm) : base(nm)

    {

        DbInfo = "Some info about database";

    }

 

    private string m_dbInfo;

    public string DbInfo

    {

        get { return m_dbInfo; }

       set { m_dbInfo = value; }

    }

}