WCF : [XmlElement, typeof] in DataMember attribute

I want to do something like :

[XmlElement("Foo1", typeof(Foo1Type))]
[XmlElement("Foo2", typeof(Foo2Type))]
public object Foo { get; set; }

But i would to do this with the DataContractSerializer for WCF. Something similar in Datamember attribute.

I aim to assign dynamically tags according to their types.

Thank you.