C#Dictionary中的下一个键

Dictionary<string, int> dictionary = new Dictionary<string, int>();
dictionary.Add("apple", 1);
dictionary.Add("banana", 2);
dictionary.Add("orange", 3);

string nextKey = "banana";
int index = 0;

foreach (string key in dictionary.Keys)
{
    if (key == nextKey)
    {
        index++;
        if (index< dictionary.Keys.Count)
        {
            nextKey = dictionary.Keys.ElementAt(index);
            break;
        }
        else
        {
            nextKey = dictionary.Keys.ElementAt(0);
            break;
        }
    }
}

Console.WriteLine("Next key: " + nextKey);