How to serialize/deserialize class-wrapper of IList collection?

Question

I have base class Control , which contains a property public ControlCollection Controls; :

public abstract class Control { 
    ...
    public virtual string Name { get: set; }
    public ControlCollection Controls;
    public Control parent = null;
    ...
}

ControlCollection is my own class, which implemets IList<Control> :

public sealed class ControlCollection : IList<Control>, IMySerializable {       
    public int Count => _controls.Count;
    public bool IsReadOnly { get; } = false;
    public Control Parent;

    private List<Control> _controls = new List<Control>();

    public ControlCollection(Control parent) {
        Parent = parent ?? throw new ArgumentNullException("parent");
    }

    public Control this[int index] {
        get => _controls[index];
        set => _controls[index] = value;
    }

    public void Add(Control child) {
        child.parent = Parent;
        _controls.Add(child);
    }

    ...
}

If I change a type of property Controls from ControlCollection to List<Control> , then code below will form a correct XML file

// temp data
Control rootObj = new Button();  rootObj.Name = "111";
Control obj2 = new Label();   obj2.Name = "222";
Control obj3 = new Button();  obj3.Name = "333";    
rootObj.Controls.Add(obj2); 
rootObj.Controls.Add(obj3);

List<Type> list = new List<Type>();
rootObj.Controls.ForEach(child => child.DoActionWithChildren(node => {
    list.Add(node.GetType());
}));

list.Add(typeof(Button));
list = list.Distinct().ToList();

// trying to set xml attributes. 'Controls' property will be a root of collection
var attributes = new XmlAttributes();
list.ForEach(t => attributes.XmlArrayItems.Add(new XmlArrayItemAttribute(t)));
var attrOverride = new XmlAttributeOverrides();
attrOverride.Add(typeof(Control), "Controls", attributes); 

// save data to file    
using(StreamWriter sw = new StreamWriter("path/to/xml/file.xml", false, Encoding.UTF8)) {
    XmlSerializer xs = new XmlSerializer(typeof(Control), attrOverride);        
    XmlSerializerNamespaces ns = new XmlSerializerNamespaces();
    ns.Add(string.Empty, string.Empty);
    xs.Serialize(sw, rootObj, ns);  
}

/* ---------------------- */
output:

<?xml version="1.0" encoding="utf-8"?>
<Control d1p1:type="Button" xmlns:d1p1="http://www.w3.org/2001/XMLSchema-instance">
  <Controls>
    <Control d1p1:type="Label">
      <Controls />      
      <Name>22222</Name>
    </Control>
    <Control d1p1:type="Button">
      <Controls />
      <Name>32333</Name>      
    </Control>
  </Controls>  
  <Name>1111</Name>  
</Control>

But if a type of property Controls is ControlCollection , then XML will be cut off:

<?xml version="1.0" encoding="utf-8"?>
<Button>
  <Controls>
    <Control d3p1:type="Label" xmlns:d3p1="http://www.w3.org/2001/XMLSchema-instance">
      <Controls />

I tried to change the type: attrOverride.Add(typeof(ControlCollection), "Controls", attributes); , but this doesn't work.

---

What should I do to serialize ControlCollection properly? And what should I know to properly deserialize it afterwards?

Answer 1

Well, I fixed it. It turned out that I had a circular reference because of a property public Control parent = null; in my base class. I wrote an attribute [XmlIgnore] and it worked, even with attrOverride.Add(typeof(ControlCollection), "Controls", attributes);

The reason why I didn't see this error is that my original project is a Unity project. And Unity didn't show me that error. When I made a simple C# Console application - it showed me that error. It's sad but true.