List<T>.GetRange

Question

hi

I was just working with List<T>.GetRange on your online c# compiler and it seems to be inconsistent when I input "list.GetRange(0,list.Count)" I receive the whole list as I should. But when I input " list.GetRange(1,list.Count)" I receive an out of bounds exception which I managed to solve by writing " list.GetRange(1,list.Count-2)" in order to get the range that I want.

Is this an intentional feature or a bug?

thanks for your time

Answer 1

As designed. Assume the list has 10 elements, with index from 0 to 9

list.GetRange(0, 10) // returns elements at indexes 0,1,2,3,4,5,6,7,8,9
list.GetRange(1, 10) // returns elements at indexes 1,2,3,4,5,6,7,8,9,10. List[10] is out of range.

Answer 2

See my .NET Fiddle

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

namespace ConsoleApp1
{
    public class Program
    {
        public static void Main()
        {
            var monthNames = Enumerable.Range(1, 12)
                .Select((index) => DateTimeFormatInfo.CurrentInfo.GetMonthName(index)).ToList();

            Index indexer = new Index(monthNames.FindIndex(item => item.Equals("april", 
                StringComparison.OrdinalIgnoreCase)));

            var fourMonths = monthNames.ByIndex(indexer.Value, 4);

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

            Console.WriteLine("");

            List<int> list = new() { 1, 2, 3, 4, 5 };

            Console.WriteLine($"list[^1] => {list[^1]}");
            Console.WriteLine("");
            var monthNamesArray = Enumerable.Range(1, 12).Select((index) =>
                DateTimeFormatInfo.CurrentInfo.GetMonthName(index)).ToArray();

            Range firstFourRange = ..4;
            Console.WriteLine(string.Join(",", monthNamesArray[firstFourRange]));
        }
    }

    static class Extensions
    {
        public static List<T> ByIndex<T>(this List<T> value, int startIndex, int endIndex) => 
            value.GetRange(startIndex, endIndex);
    }
}