using System;

public class IndexedItem

{

    private static int _nextIndex = 0;

​

    public int Value { get; set; }

    public int Index { get; private set; }

​

    public IndexedItem(int value)

    {

        Value = value;

        Index = GetNextIndex();

    }

​

    public static int GetNextIndex()

    {

        return _nextIndex++;

    }

​

    // Optional: Reset the index for testing purposes.  Not generally needed in production.

    public static void ResetNextIndex()

    {

        _nextIndex = 0;

    }

    public static void Main()

    {

        var item1 = new IndexedItem(10);

        var item2 = new IndexedItem(-20);

        var item3 = new IndexedItem(30);

        Console.WriteLine($"Index: {item1.Index}, Value: {item1.Value}");

        Console.WriteLine($"Index: {item2.Index}, Value: {item2.Value}");

        Console.WriteLine($"Index: {item3.Index}, Value: {item3.Value}");

    }

}