Writing base class settings in a base class, called from a derived class.

[DaveTran]

I have two settings classes one abstract base class from which the second settings class derives

    public abstract class BaseFooSettings
    {
        public int a;
        public int b;
        public float c;
    }

    public class DerivedBarSettings : BaseFooSettings
    {
        public float d;
    }

I then have two classes one base class and a second class that derives from the first

    public abstract class BaseFoo
    {
        private int a = 0;
        private int b = 1;
        private float c = 1.2f;

        public BaseFoo() { }

        public abstract BaseFooSettings WriteSettings();

        public int A
        {
            get { return a; }
            set { a = value; }
        }

        public int B
        {
            get { return b; }
            set { c = value; }
        }

        public float C
        {
            get { return c; }
            set { c = value; }
        }
    }

        public class DerivedBar : BaseFoo
    {
        float d = 0.9f;

        public DerivedBar()
            : base() { }
    }

With this setup it is easy to save the state of the derived class by saving its settings using the following method

    public override BaseFooSettings WriteSettings()
    {
        DerivedBarSettings settings = new DerivedBarSettings();

        settings.a = A;
        settings.b = B;
        settings.c = C;
        settings.d = d;

        return settings;
    }

The problem with this approach is that all the settings must be explicitely set in the derived class and not just the local or derived class settings.

What I would like to do is something akin to

    public override BaseFooSettings WriteSettings()
    {
        DerivedBarSettings settings = new DerivedBarSettings();

        // Write base settings
        WriteBaseFooSettings(ref settings);

        // Write derived/local settings
        settings.d = d;

        return settings;
    }

The base class would then look like

    public abstract class BaseFoo
    {
        private int a = 0;
        private int b = 1;
        private float c = 1.2f;

        public BaseFoo() { }

        public abstract BaseFooSettings WriteSettings();

        protected void WriteBaseFooSettings(ref BaseFooSettings settings)
        {
            settings.a = a;
            settings.b = b;
            settings.c = c;
        }

        public int A
        {
            get { return a; }
            set { a = value; }
        }

        public int B
        {
            get { return b; }
            set { c = value; }
        }

        public float C
        {
            get { return c; }
            set { c = value; }
        }
    }

This approach doesn't work though as I cannot convert from 'ref DerivedBarSettings' to 'ref BaseFooSettings'.

How can I implement the new approach correctly?