Apply indexing in binary search for string

Question

I'm getting the error of not being able to apply indexing, but I'm not sure how establish a 'bounds'(algebraically) for the BinarySearch to find a string. It's apparent that

     if (item > N[mid])

can't function because item is a string. How do I find item in this?:

    public static int BinarySearch(string[] name, string item)
    {

        int min = 0;
        int N = name.Length;
        int max = N - 1;
        do
        {
            int mid = (min + max) / 2;
            if (item > N[mid])
                min = mid + 1;
            else
                max = mid - 1;
            if (name[mid] == item)
                return mid;
            //if (min > max)
            //   break;
        } while (min <= max);
        return -1;
    }

and trying to appease it with something like this

   public static int BinarySearch(string[] name, string searchKeyword)
    {

        int min = 0; //=0
        int N = name.Length;  //.Length
        int max = N - 1;
        int S = searchKeyword.Length;



        do
        {
            int mid = (min + max) / 2;
            if (S > N[mid])
                min = mid + 1;
            else
                max = mid - 1;
            if (name[mid] == S)
                return mid;
            //if (min > max)
            //   break;
        } while (min <= max);
        return -1;
    }

Answer 1

You cannot use the > operator in a string because C# does not know what do you mean when saying that a string is bigger than another. Do you compare by length, alphabetical order...?.

If you want to sort them alphabetically, use the String.Compare method instead:

public static int BinarySearch(string[] name, string item)
{

    int min = 0;
    int N = name.Length;
    int max = N - 1;
    do
    {
        int mid = (min + max) / 2;
        if (String.Compare(item, name[mid]) > 0)
            min = mid + 1;
        else
            max = mid - 1;
        if (String.Compare(item, name[mid]) == 0)
            return mid;            //if (min > max)
        //   break;
    } while (min <= max);
    return -1;
}