using System;

using System.Globalization;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

​

        var list = new List<double?>() { null, null, null};

        //Console.WriteLine(list.Select(e=>e).DefaultIfEmpty().Average());

        Console.WriteLine(list.DefaultIfEmpty(0).Average());

        Console.WriteLine(list.DefaultIfEmpty(0).Max());

​

        var list2 = new List<double?>() { null, null, null, 0, null, 23};

        Console.WriteLine(list2.DefaultIfEmpty(0).Average());

        Console.WriteLine(list2.DefaultIfEmpty(0).Max());

​

        Console.WriteLine("END");

    }

}