using System;

using System.IO;

using System.Text;

using System.Windows;

using System.Xml;

using System.Xml.Serialization;

​

public class Program

{

    public static void Main()

    {

        ResponseBase result1 = Deserialize("<?xml version=\"1.0\"?>\r\n  <root>\r\n    <elementOne>101</elementOne>\r\n    <elementTwo>10</elementTwo>\r\n  </root>");

        ResponseBase result2 = Deserialize("<?xml version=\"1.0\"?>\r\n  <root>\r\n    <elementOne>101</elementOne>\r\n    <elementTwo>10</elementTwo>\r\n    <elementThree>10</elementThree>\r\n  </root>");

        PrintResult(result1);

        PrintResult(result2);

    }

    private static void PrintResult(ResponseBase result)

    {

        if(result is DerivedOneClass)

        {

            DerivedOneClass derived = (DerivedOneClass)result;

            Console.WriteLine("Result is of type 'DerivedOneClass': {0}, {1}", derived.ElementOne, derived.ElementTwo);

        }

        else if(result is DerivedTwoClass)

        {

            DerivedTwoClass derived = (DerivedTwoClass)result;

            Console.WriteLine("Result is of type 'DerivedTwoClass': {0}, {1}, {2}", derived.ElementOne, derived.ElementTwo, derived.ElementThree);

        }

    }

    private static ResponseBase Deserialize(string xml)

    {

        MemoryStream stream = new MemoryStream(Encoding.UTF8.GetBytes(xml));

        XmlSerializer serializer = new XmlSerializer(typeof(ResponseBase));

        XmlDocument document = new XmlDocument();

        document.Load(stream);

        AddTypeDefinition(document);

        XmlReader reader = new XmlNodeReader(document);

        ResponseBase result = serializer.Deserialize(reader) as ResponseBase;

        return result;

    }

    private static void AddTypeDefinition(XmlDocument document)

        {

            const string xsiNamespaceUri = "http://www.w3.org/2001/XMLSchema-instance";

​

            XmlNode node = document.SelectSingleNode("root");

            if (node == null) return;

​

            var typeAttribute = node.Attributes["type", xsiNamespaceUri];

            if (typeAttribute != null) return;

​

            string type = "DerivedOneClass";

​

            XmlNodeList nodes = node.SelectNodes("//elementThree");

            if (nodes != null && nodes.Count > 0)

                type = "DerivedTwoClass";

​

            XmlAttribute attribute = document.CreateAttribute("xsi", "type", xsiNamespaceUri);

            attribute.Value = type;

            node.Attributes.Append(attribute);

        }

​

        [XmlInclude(typeof(DerivedOneClass))]

        [XmlInclude(typeof(DerivedTwoClass))]

        [XmlRoot(ElementName = "root")]

        public class ResponseBase

        {

        }

​

        public class DerivedOneClass: ResponseBase

        {

          [XmlElementAttribute("elementOne")]

          public string ElementOne {get; set;}

          [XmlElementAttribute("elementTwo")]

          public string ElementTwo {get; set;}

        }

​

        public class DerivedTwoClass: ResponseBase

        {

          [XmlElementAttribute("elementOne")]

          public string ElementOne {get; set;}

          [XmlElementAttribute("elementTwo")]

          public string ElementTwo {get; set;}

          [XmlElementAttribute("elementThree")]

          public string ElementThree {get; set;}

        }

}