Code Inspection: Index from end must be greater than zero

The reverse index operator ^ introduced in C# 8.0 might lead to a mistake of referring to the last element with ^0, the same way as you refer to the first element 0. However, the index from end is designed to start with 1, and therefore using ^0 as an index will result in an IndexOutOfRangeException in runtime.

This StackOverflow answer provides a good explanation of why index from end stars with 1 and not with 0.

To fix this problem, replace ^0 with ^1 in the index.

            
void Sample()
{
    var numbers = new[] { "one", "two", "three" };
    var three = numbers[^0];
    Console.WriteLine(three);
}

        

            
void Sample()
{
    var numbers = new[] { "one", "two", "three" };
    var three = numbers[^1];
    Console.WriteLine(three);
}

        

Last modified: 21 March 2024