c#遍历的两种方式 for和foreach
for： 需要指定首位数据、末尾数据、数据长度； for遍历语句中可以改变数据的值； 遍历规则可以自定义，灵活性较高
foreach： 需要实现ienumerator接口； 在遍历中不可以改变数据的值； 遍历规则只能是'++' ； 但查询效率较高
Dictionary遍历方式：
Dictionary<string, int> list = new Dictionary<string, int>(); list.Add("d", 1); //3.0以上版本 foreach (var item in list) { Console.WriteLine(item.Key + item.Value); } //KeyValuePair<T,K> foreach (KeyValuePair<string, int> kv in list) { Console.WriteLine(kv.Key + kv.Value); } //通过键的集合取 foreach (string key in list.Keys) { Console.WriteLine(key + list[key]); } //直接取值 foreach (int val in list.Values) { Console.WriteLine(val); } //非要采用for的方法也可 List<string> test = new List<string>(list.Keys); for (int i = 0; i < list.Count; i++) { Console.WriteLine(test[i] + list[test[i]]); } |
List排序：
Hashtable ht=new Hashtable(); ht.Add("E","e"); ht.Add("A","a"); ht.Add("C","c"); ht.Add("B","b"); ArrayList lst=new ArrayList(ht.Keys); lst.Sort(); foreach(string key in lst) { listBox1.Items.Add("key:" + key + " vlaue:"+ht[key]); } |
Dictionary排序
排序思路：
1>用一个List保存Dictionary的数据
2>对新的List进行排序
3>从List获取排序好的值，重新添加进Dictionary
protected Dictionary<string, int> SortDictionary_Desc(Dictionary<string, int> dic) { List<KeyValuePair<string, int>> myList = new List<KeyValuePair<string, int>>(dic); myList.Sort(delegate(KeyValuePair<string, int> s1, KeyValuePair<string, int> s2) { return s2.Value.CompareTo(s1.Value); }); dic.Clear(); foreach (KeyValuePair<string, int> pair in myList) { dic.Add(pair.Key, pair.Value); } return dic; } protected Dictionary<string, int> SortDictionary_Asc(Dictionary<string, int> dic) { List<KeyValuePair<string, int>> myList = new List<KeyValuePair<string, int>>(dic); myList.Sort(delegate(KeyValuePair<string, int> s1, KeyValuePair<string, int> s2) { return s1.Value.CompareTo(s2.Value); }); dic.Clear(); foreach (KeyValuePair<string, int> pair in myList) { dic.Add(pair.Key, pair.Value); } return dic; } |
