SortedList <K,V>上是否有下限功能？

二进制搜索SortedList.Keys集合.

开始了.这是O(log n):

private static int BinarySearch(IList list, T value)
{
    if (list == null)
        throw new ArgumentNullException("list");
    var comp = Comparer.Default;
    int lo = 0, hi = list.Count - 1;
    while (lo < hi) {
            int m = (hi + lo) / 2;  // this might overflow; be careful.
            if (comp.Compare(list[m], value) < 0) lo = m + 1;
            else hi = m - 1;
    }
    if (comp.Compare(list[lo], value) < 0) lo++;
    return lo;
}

public static int FindFirstIndexGreaterThanOrEqualTo
                          (this SortedList sortedList, T key)
{
    return BinarySearch(sortedList.Keys, key);
}