How to save CPU cycles when searching for a value in a sorted list?

Question

In CodinGame learning platform, one of the questions used as an example in a C# tutorial is this one:

The aim of this exercise is to check the presence of

Answer 1

class Answer
{
    public static bool Exists(int[] ints, int k)
    {
        int index = Array.BinarySearch(ints, k);
        if (index > -1)
        {
            return true;
        }
        else
        {
            return false;
        }
    }
    static void Main(string[] args)
    {
        int[] ints = { -9, 14, 37, 102 };
        Console.WriteLine(Answer.Exists(ints, 14)); // true
        Console.WriteLine(Answer.Exists(ints, 4)); // false
    }

}