.Net 4 brings with it the Tuple type! I have never worked with tuples in programming before and have a hard time seeing their purpose but here is an example of a tuple in C#:
什么是Tuple，在汉语上我们将其翻译为元组。Tuple的概念源于数学概念，表示有序的数据集合。在.NET中Tuple被实现为泛型类型，n-Tuple表示有n个元素的Tuple，集合的元素可以是任何类型
var tupleOne = new Tuple<int, string>(1, "Hello World");
Console.WriteLine("Tuple contains: " + tupleOne.Item1 + " and " + tupleOne.Item2);
There are also some factory methods for creating tuples:
var tupleTwo = Tuple.Create("Hello World", 2010);
var tupleThree = Tuple.Create("Hello World", 2010, new SomeClass());
Console.WriteLine("Tuple contains: " + tupleThree.Item1 + ", " + tupleThree.Item2 + " and " + tupleThree.Item3.MyProperty);
Tuple facts:
- Tuples are immutable
- Tuples are reference types
- Located in System.Tuple
- Can take up to 8 generic parameters, but can contain an infinite number of elements.
- Elements are always named Item1, Item2… Item7, Rest
See msdn for more information.
为什么要用Tuple呢？这是个值得权衡的问题，上述MyRequest类型中通过3-Tuple对需要的Request信息进行封装，我们当然也可创建一个新的struct来封装，两种方式均可胜任。然则，在实际的编程实践中，很多时候我们需要一种灵活的创建一定数据结构的类型，很多时候新的数据结构充当着“临时”角色，通过大动干戈新类型完全没有必要，而Tuple既是为此种体验而设计的。例如：
- Point {X, Y}，可以表示坐标位置的数据结构。
- Date {Year, Month, Day}，可以表示日期结构；Time {Hour, Minute, Second}，可以表示时间结构；而DateTime {Date, Time}则可以实现灵活的日期时间结构。
- Request {Name, URL, Result}，可以表示Request的若干信息。
- 。。。，随需而取。
http://technet.microsoft.com/zh-cn/library/dd387150(v=VS.95)