C# 6.0 Reflection: Extract the name of backing fields of read-only auto properties

I have a serialization mechanism in place that works on the private fields to determine what should be serialized and what not. The main idea behind the approach is to only serialize the "essence" of the data.

Example:

public class Person {
    private readonly string _firstName;
    private readonly string _lastName;

    public C1(string firstName, string lastName) {
        _firstName = firstName;
        _lastName = lastName;
    }

    public string FirstName { get { return _firstName; } }
    public string LastName { get { return _lastName; } }
    public string FullName { get { return _firstName + " " + _lastName; } }
}

A serialized example object would then look like this (JSON):

{ "firstName": "John", "lastName": "Doe" }

As you can see, serializing based on fields ensures that FullName is not serialized.

This mechanism was in place for a while now and worked flawlessly. However, with the new read-only auto properties in C# 6.0, the fields have an awkward name like e.g. <FirstName>k__BackingField.

Of course, I can update my serialization code to extract the actual property name from the backing field and use that name during serialization. What I want to know: Is this a robust solution? Or is the naming of the generated backing fields subject to change?

Note: The reason for this approach is that model classes can remain serialization-agnostic like that. I know that I could also use the [JsonIgnore] attributes to achieve the same, but I don't want to add such attributes to my model classes.