using System;

using System.Linq;

using System.Collections.Generic;

using System.Threading;

using System.Threading.Tasks;

using System.Runtime.CompilerServices;

using System.IO;

using System.Xml;

using System.Xml.Serialization;

using System.Drawing;

using System.Text.RegularExpressions;

​

public static class Program

{

    public enum A { a = 0, b = 1, c = 2 }

​

    public class AdjustSelector<T>

    {

        internal AdjustSelector() { }

​

        public Func<T, int, bool> ByPosition(int position) =>

            (_, pos) => position == pos;

​

        public Func<T, int, bool> ByProp(Func<T, bool> predicate) =>

            (obj, _) => predicate(obj);

    }

​

    public static IEnumerable<T> Adjust<T>(this IEnumerable<T> @this, Func<T, int, bool> shouldReplace, T replacement) =>

        @this.Select((obj, pos) =>

                     shouldReplace(obj, pos)

                     ? replacement

                     : obj);

​

    public static void Main()

    {

        Console.WriteLine("App started.");

​

        uint a = uint.MaxValue;

        uint b = a + 1;

        //Test1();

        //Test2((A) 3);

        Test3();

​

        Console.WriteLine("App finished.");

    }

​

    public static void Test1()

    {

        var arrayOfStuff = new[] { "a", "b", "c", "d" };

        var array2 = arrayOfStuff.Adjust((x, i) => i == 2, "z");

        Console.WriteLine(string.Join(", ", array2));

    }

​

    public static void Test2(A value)

    {

        string s = value switch

        {

                A.a => "a",

                A.b => "b",

                A.c => "c"

        };

        Console.WriteLine(s);

    }

​

    public static void Test3()

    {

        float? a = null;

        int? b = null;

        Console.WriteLine(((int?) a));

    }

​

}

​