C# Serialize Object instance to XML

Question

I got a little problem with serializing object instance and let some pseudo code speak for itself:

List<A> ListOfA = new List<A>();

[Serializable]
public class A
{
public Object Instance;
...
}

[Serializable]
public class B
{
    public String SomeAttribute = "example"; 
}

// This will be called:

void Serialize()
{
    var a = new A();
    a.Instance = new B();
    ListOfA.Add(a);

 // a.Instance = new String("test"); works but List<String>, B, ... throws Invalid Operation Exception when serializing:

    using (TextWriter textWriter = new StreamWriter(filePath, false))
    {
        var xmlSerializer = new XmlSerializer(ListOfA.GetType());
        xmlSerializer.Serialize(textWriter, ListOfA );
    }
}

Anyone have a solution for this?

I have tried to use XmlInclude without any result.

Is it even possible to serialize Object without knowing its type?

Answer 1

Try:

[XmlInclude(typeof(B))]
public class A {
  public Object Instance;
}

Btw. [Serializable] is useless for xml serialization.

Answer 2

Thx for your fast response but I did find solution for my problem by giving second parameter to XmlSerializer:

var xmlSerializer = new XmlSerializer(ListOfA.GetType(), new Type[] { typeof(B) });

And this way I don't have to add [XmlInclude(typeof(B))] to class A...