How to map property of type `Object` with different datatypes to a corresponding classtype?

问题

I have two classes:

public class A{
[System.Xml.Serialization.XmlElementAttribute("type1", typeof(XMLItemType1), IsNullable=true)]
[System.Xml.Serialization.XmlElementAttribute("type2", typeof(XMLItemType2), IsNullable=true)]
public object Item { get; set; }
}

public class B{
public object Item { get; set; }
}

Mapping is created as follows:

AutoMapper.Mapper.CreateMap<A, B>()
.ForMember(domainObject => domainObject.Item ,
metaData => metaData.MapFrom(xmlObject => xmlObject.Item ));


AutoMapper.Mapper.CreateMap<XMLItemType1, XMLObjectType1>();
AutoMapper.Mapper.CreateMap<XMLItemType2, XMLObjectType2>();

AutoMapper.Mapper.Map<A, B>(data);            

But the output property of B class Item is of type XMLItemType1 instead of XMLObjectType1.

How can I make sure that after mapping Item is of type XMLObjectType1 or XMLObjectType2?

来源：https://stackoverflow.com/questions/32689294/how-to-map-property-of-type-object-with-different-datatypes-to-a-corresponding