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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;
}
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原文地址：http://www.cnblogs.com/candyzhmm/p/5612097.html
