[C#] BinarySearch for index in sorted int array

//Don't forget to sort the array
public static int BinarySearchFindIndex(int[] array, int target)
{
    int start = 0;
    int end = array.Length - 1;
    int value, mid = 0;
    while (start != end)
    {
        mid = start + (end - start) / 2;
        value = array[mid];

        if (value == target)
            return mid;
        else if (value > target)
            end = mid - 1;
        else if (value < target)
            start = mid + 1;
    }
    if (array[mid] == target)
        return mid;
    else
        return -404; //Number does not exist in the array;
}