BinarySearch.cs

public static int BinarySearch(int[] arr, int k)
{
    var minIndex = 0;
    var maxIndex = arr.Length - 1;

    while (minIndex <= maxIndex)
    {
        var mid = (minIndex + maxIndex) / 2;
	    
        if (k == arr[mid])
        {
	    return mid;
	}

	if (k < arr[mid])
	{
	    maxIndex = mid - 1;
	}
	else
	{
	    minIndex = mid + 1;	
	}
    }
	
    return -1;
}