OrderedDictionary和Dictionary

Question

我正在寻找一种方法来按照添加它们的顺序Dictionary枚举它KeyValuePair.现在,Dictionary的文档明确指出:

出于枚举的目的,字典中的每个项目都被视为KeyValuePair<TKey, TValue>表示值及其键的结构.返回项的顺序未定义.

我发现我需要的是一个OrderedDictionary,但我是怀疑论者,我决定亲自尝试:

OrderedDictionary od = new OrderedDictionary();
Dictionary<String, String> d = new Dictionary<String, String>();

for (int i = 0; i < 10; i++)
{
    od.Add("key" + i, "value" + i);
    d.Add("key" + i, "value" + i);
}

System.Console.WriteLine("OrderedDictionary");
foreach (DictionaryEntry de in od) {
    System.Console.WriteLine(de.Key + ", " + de.Value);
}

System.Console.WriteLine("Dictionary");
foreach (var tmp in d) {
    System.Console.WriteLine(tmp.Key + ", " + tmp.Value);
}

输出:

OrderedDictionary
key0, value0
key1, value1
key2, value2
...

Dictionary
key0, value0
key1, value1
key2, value2
...

正如您所看到的,两者都是有序的,并提出了两个问题:
在哪种情况下,Dictionary给出与添加值的顺序不同的顺序？我的第一个foreach循环是否确保我以KeyValuePair相同的顺序检索我,或者我是否必须使用索引？

Answer 1

你做错了.您不仅需要按顺序将值插入到字典中,还需要删除一些元素,并在此之后查看订单的更改方式.下一代码演示了这个:

OrderedDictionary od = new OrderedDictionary();
Dictionary<String, String> d = new Dictionary<String, String>();
Random r = new Random();

for (int i = 0; i < 10; i++)
{
    od.Add("key" + i, "value" + i);
    d.Add("key" + i, "value" + i);
    if (i % 3 == 0)
    {
        od.Remove("key" + r.Next(d.Count));
        d.Remove("key" + r.Next(d.Count));
    }
}

System.Console.WriteLine("OrderedDictionary");
foreach (DictionaryEntry de in od) {
    System.Console.WriteLine(de.Key + ", " +de.Value);
}

System.Console.WriteLine("Dictionary");
foreach (var tmp in d) {
    System.Console.WriteLine(tmp.Key + ", " + tmp.Value);
}

打印类似的东西(OrderedDictionary总是有序):

OrderedDictionary
key3, value3
key5, value5
key6, value6
key7, value7
key8, value8
key9, value9
Dictionary
key7, value7
key4, value4
key3, value3
key5, value5
key6, value6
key8, value8
key9, value9