.cs

            int? shape = null;
            Shape shape = null;
            Shape shape = new Rectangle
            {
                Width = 100,
                Height = 100,
            };

            //this is valid for all the above
            var t = shape.Map(x => x.ToString());
            
    public static class FunctionalExt
    {
        public static T1 Map<T, T1>(this T @this, Func<T, T1> f) =>
                       @this switch
                       {
                           T value => f(value),
                           null => default,
                       };
       
    }