Generic Binary Search in C#

Question

Below is my Generic Binary Search. It works okay with the integers type array (it finds all the elements in it). But the problem arises when I use a string array to find any

Answer 1

//Binary search recursive method

    public void BinarySearch(int[] input,int key,int start,int end)
    {
        int index=-1;
        int mid=(start+end)/2;
        if (input[start] <= key && key <= input[end])
        {
            if (key < input[mid])
                BinarySearch(input, key, start, mid);
            else if (key > input[mid])
                BinarySearch(input, key, mid + 1, end);
            else if (key == input[mid])
                index = mid;
            if (index != -1)
                Console.WriteLine("got it at " + index);
        }
    }  

     int[] input4 = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };   
     BinarySearch(input4, 1, 0, 8);