Polymorphism with Serialized Data

问题

I am trying to use Polymorphism with data that is to be serialized and deserialized. However, it seems that the polymorphic properties are being lost on serialization:

// Serialize
[System.Serializable]
public ParentClass()
{
  public string someString = "a string";
}
[System.Serializable]
public ChildClass() : ParentClass
{
  public int someInt;
  public ChildClass(int _someInt)
  {
    someInt = _someInt;
  }
}

List<ParentClass> list = new List<ParentClass>();
list.Add(new ChildClass(5));

// Data is serialized

// Data is deserialized

Debug.Log(list[0].someString);
// Output: a string; Works as intended

Debug.Log((list[0] as ChildClass).someInt));
// Null Reference Exception

How can you properly serialize these classes in this case?

来源：https://stackoverflow.com/questions/10362513/polymorphism-with-serialized-data