csharp-search-binary

public static class ListExtensions
{
    static int Find<TListInt>(this TListInt list, int first, int last, int value)
        where TListInt : IList<int>
    {
        int diff = ( last - first );
        if (diff == 0)
        {
            if (list[first] == value)
            {
                return last;
            }
            return -1;
        }
        int mid = first + ( diff / 2 );
        int midValue = list[mid];
        if (midValue == value)
        {
            return mid;
        }
        else if (midValue > value)
        {
            if (--mid < first)
            {
                return -1;
            }
            return list.Find(first, mid, value);
        }
        else
        {
            if (++mid > last)
            {
                return -1;
            }
            return list.Find(mid, last, value);
        }
    }

    public static int Find<TListInt>(this TListInt list, int value)
        where TListInt : IList<int>
    {
        if (list != null && list.Count > 0)
        {
            return list.Find(0, list.Count - 1, value);
        }
        return -1;
    }
}