DictionaryEntry 结构

定义可设置或检索的字典键/值对。
foreach (DictionaryEntry de in myHashtable) {...}
 
foreach 语句是对枚举数的包装，它只允许从集合中读取，不允许写入集合。
 
Key是键
Value是值
Hashtable 内的每一组对象就是一个DictionaryEntry 
例如我们要循环hashtable 
foreach (DictionaryEntry de in myHashtable) {...} 
Hashtable就是一个DictionaryEntry的集合
在一个Hashtable中
Key的值是不可以重复的，必须是唯一的，但Value的值可以是重复的
在查询时，Key担当索引的功能 

// A simple example for the DictionaryEntry structure. using System; using System.Collections; class Example { public static void Main() { // Create a new hash table. // Hashtable openWith = new Hashtable(); // Add some elements to the hash table. There are no // duplicate keys, but some of the values are duplicates. openWith.Add("txt", "notepad.exe"); openWith.Add("bmp", "paint.exe"); openWith.Add("dib", "paint.exe"); openWith.Add("rtf", "wordpad.exe"); // When you use foreach to enumerate hash table elements, // the elements are retrieved as KeyValuePair objects. Console.WriteLine(); foreach (DictionaryEntry de in openWith) { Console.WriteLine("Key = {0}, Value = {1}", de.Key, de.Value); } } } /* This code example produces output similar to the following: Key = rtf, Value = wordpad.exe Key = txt, Value = notepad.exe Key = dib, Value = paint.exe Key = bmp, Value = paint.exe */