Sample to pop straight into SharpLab to see how the indices and range syntax introduced in C# 8 gets lowered

IndiceAndRangeCsharp8Example.cs

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        var payments = new List<Payment>
        {
            new Payment { Id = 1, Amount = 100.00m },
            new Payment { Id = 2, Amount = 150.50m },
            new Payment { Id = 3, Amount = 200.75m },
            new Payment { Id = 4, Amount = 50.25m },
            new Payment { Id = 5, Amount = 300.00m }
        };
    }

    static void OutputIndiceNormal(List<Payment> payments)
    {
        var lastPayment = payments[payments.Count - 1];
    }

    static void OutputIndiceSimplified(List<Payment> payments)
    {
        var lastPayment = payments[^1];
    }

    static void OutputRangeNormal(List<Payment> payments)
    {
        var paymentsSubset = payments.Skip(0).Take(3).ToList();
    }

    static void OutputRangeSimplified(List<Payment> payments)
    {
        var paymentsSubset = payments[0..3];   }
    }

class Payment
{
    public int Id { get; set; }
    public decimal Amount { get; set; }
}