I have encounter some code that inherits SortedSet<T>, for example

public class Dius : SortedSet<int> 
{
	int a; 
	string b; 
}

I need to do serializations on this object. If you use C# DataContract Serializer or XML Serializer, you will find that only contents in SortedSet<int> will be serialized. Neither of the extra properties a or b will be serialized. This is because the class inherits a class from either IEnumerable or ICollection.

See

• https://stackoverflow.com/questions/666054/c-sharp-inheriting-generic-collection-and-serialization
• https://stackoverflow.com/questions/1797947/xmlserializer-doesnt-serialize-everything-in-my-class
• https://stackoverflow.com/questions/55301839/serializing-class-inherited-from-list-using-datacontractserializer-does-not-se
• https://stackoverflow.com/questions/5069099/when-a-class-is-inherited-from-list-xmlserializer-doesnt-serialize-other-att
• https://stackoverflow.com/questions/25103608/serialize-sorted-set-members
• https://stackoverflow.com/questions/377486/xmlserialize-a-custom-collection-with-an-attribute
• https://stackoverflow.com/questions/25251798/deserializing-xml-in-object-using-datacontractserializer
• https://docs.microsoft.com/en-us/dotnet/standard/serialization/introducing-xml-serialization#items-that-can-be-serialized
• and two more below

For JSON .NET

• https://stackoverflow.com/questions/5863496/is-there-any-way-to-json-net-serialize-a-subclass-of-listt-that-also-has-extra

Basically, in most of these answers, the alternative is to redefine the class like this

public class Dius 
{
	int a; 
	string b; 
	SortedSet<int> collection; 
}

However, I CANNOT redefine the class definition in this problem. So I found another workaround, see

• https://stackoverflow.com/questions/3431843/serialization-of-class-derived-from-list-using-datacontract/3432106#3432106
• https://stackoverflow.com/questions/1285018/datacontractserializer-not-serializing-member-of-class-that-inherits-iserializab

The idea is that, for DataContract Serializer, it will use customized IXmlSerializable interface methods to serialize the object.

This time, we define a Dius_Wrapper class that looks like the second definition above, and let the original class Dius implements the interface IXmlSerializable. The interface methods and the wrapper class will look like this

// All the code below is within class Dius, which implements IXmlSerializable
[DataContract]
private class Dius_Wrapper
{
    [DataMember]
    public int a;
    [DataMember]
    public string b;
    [DataMember]
    public SortedSet<Yem> collection;
}

public XmlSchema GetSchema()
{
    return null; 
}

public void ReadXml(XmlReader reader)
{
    List<Type> knownTypes = new List<Type>() { typeof(Dius) };
    DataContractSerializer ser = 
		new DataContractSerializer(typeof(Dius_Wrapper), knownTypes);
    reader.ReadString();
    Dius_Wrapper dw = (Dius_Wrapper)ser.ReadObject(reader, true);

    this.Clear();
    this.UnionWith(dw.collection);
    this.a = dw.a;
    this.b = dw.b;
}

public void WriteXml(XmlWriter writer)
{
    Dius_Wrapper dw = new Dius_Wrapper() 
	{ 
		collection = new SortedSet<Yem>(this), 
		a = this.a, 
		b = this.b 
	};
    List<Type> knownTypes = new List<Type>() { typeof(Dius) };
    DataContractSerializer ser = 
		new DataContractSerializer(typeof(Dius_Wrapper), knownTypes);
    ser.WriteObject(writer, dw);
}

This may not be the best solution, but it solves the problem without significant changes to the original code. You may download the code and run it yourself. Although I wrote this code for SortedSet<>, it should also work with other IEnumerable, such as List<>, hopefully.

MIT. Use at your own risk.