How to serialize a derived class as its base class

.net, serialization

Solution

You'll have to pass GetType(DerivedClass) to the serializer constructor, it must match the type of the object you serialize. You can use the `<XmlRoot>` attribute to rename to the root element. This example code worked as intended:

using System;
using System.Xml.Serialization;
using System.IO;

class Program {
  static void Main(string[] args) {
    var obj = new DerivedClass();
    obj.Prop = 42;
    var xs = new XmlSerializer(typeof(DerivedClass));
    var sw = new StringWriter();
    xs.Serialize(sw, obj);
    Console.WriteLine(sw.ToString());

    var sr = new StringReader(sw.ToString());
    var obj2 = (BaseClass)xs.Deserialize(sr);
    Console.ReadLine();
  }
}

public class BaseClass {
  public int Prop { get; set; }
}
[XmlRoot("BaseClass")]
public class DerivedClass : BaseClass { }

Problem

I have a derived class that adds only methods to a base class. How can one serialize the derived class so that it matches the serialization of the base class? i.e. The serialized xml of the derived class should look like: ``` <BaseClass> ... </BaseClass> ``` e.g. The following will throw an `InvalidOperationException` The type DerivedClass was not expected. Use the XmlInclude or SoapInclude attribute to specify types that are not known statically. ``` Class BaseClass {} Class DerivedClass : BaseClass {} DerivedClass derived = new DerivedClass(); StreamWriter stream = new StreamWriter("output file path"); XmlSerializer serializer = new XmlSerializer(GetType(BaseClass)); serializer(stream, derived); ```

Original source