如何将List<Tuple<int，int>>转换为Dictionary<int，List<int>>？

List<Tuple<int, int>> tupleList = new List<Tuple<int, int>>();
tupleList.Add(new Tuple<int, int>(1, 10));
tupleList.Add(new Tuple<int, int>(2, 20));
tupleList.Add(new Tuple<int, int>(1, 30));
tupleList.Add(new Tuple<int, int>(3, 40));

Dictionary<int, List<int>> dictionary = new Dictionary<int, List<int>>();

foreach (var tuple in tupleList)
{
    int key = tuple.Item1;
    int value = tuple.Item2;

    if (dictionary.ContainsKey(key))
    {
        dictionary[key].Add(value);
    }
    else
    {
        dictionary[key] = new List<int> { value };
    }
}

Key: 1, Value: [10, 30]
Key: 2, Value: [20]
Key: 3, Value: [40]