How to serialize property of type Object with XmlSerializer

Question

I have a property:

public object Tag

but it can contain finite number of types, unfortunately without base type (except object type). But when I serialize the object with this property, it doesn't get serialized. Is there a way to instruct XmlSerializer with possible types?

Answer 1

I don't recommend this, but yes, you can use [XmlElement] etc to tell it about multiple candidate types for a member:

public class Test
{
    private static void Main()
    {
        var ser = new XmlSerializer(typeof (Test));
        var obj = new Test {Value = "abc"};
        ser.Serialize(Console.Out, obj);
        obj = new Test { Value = 123 };
        ser.Serialize(Console.Out, obj);
        obj = new Test { Value = 456.7F };
        ser.Serialize(Console.Out, obj);
    }

    [XmlElement("a", Type = typeof(int))]
    [XmlElement("b", Type = typeof(string))]
    [XmlElement("c", Type = typeof(float))]
    public object Value { get; set; }
}

The important bits of the output (ignoring all the xmlns / <?xml> etc) are:

<Test>
  <b>abc</b>
</Test>

<Test>
  <a>123</a>
</Test>

<Test>
  <c>456.7</c>
</Test>