blocks|key|3133684|text|是的，根据这个MSDN+Forum+thread|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3133685|entityMap|0|LINK|mutability|MUTABLE|url|http://social.msdn.microsoft.com/Forums/en-US/netfxbcl/thread/24618c6e-3efe-4687-8ee3-74f47c18b997/^0|7|H|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Yes according to this <a href="http://social.msdn.microsoft.com/Forums/en-US/netfxbcl/thread/24618c6e-3efe-4687-8ee3-74f47c18b997/" rel="nofollow noreferrer">MSDN Forum thread</a>

blocks|key|355680|text|是。但这不是规范的一部分。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|355681|参考：List+Class|offset|length|355682|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx^0|0|3|A|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

Yes. But it's not part of the specification.

Ref: <a href="http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx" rel="nofollow noreferrer">List Class</a>

blocks|key|353162|text|该列表是基于索引的，并且新项目将始终添加到列表的末尾。您可以在某个索引处插入项目，以便下一个项目将移动一个位置。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|353163|所以，是的，，你可以这样安全地使用它……|353164|353165|+List(T)类是ArrayList类的泛型等价物。它使用一个数组实现IList(T)泛型接口，该数组的大小可以根据需要动态增加。|blockquote|353166|353167|可以使用整数索引访问此集合中的元素。此集合中的索引是从零开始的。|353168|不保证对列表(T)进行排序。在执行需要对列表(T)进行排序的操作(如BinarySearch)之前，必须对列表(T)进行排序。|353169|只要集合未被修改，列表(T)就可以同时支持多个读取器。枚举集合本质上不是线程安全的过程。在枚举与一个或多个写访问冲突的极少数情况下，确保线程安全的唯一方法是在整个枚举期间锁定集合。若要允许多个线程访问集合以进行读写，您必须实现自己的同步。|353170|353171|你可以在MSDN上阅读更多关于它的内容。|offset|length|353172|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx^0|0|0|0|0|0|0|0|0|0|4|4|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|12|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|13|8|@]|9|@]|A|$]]|$1|E|3|F|5|G|7|14|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|15|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|16|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|17|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|18|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|19|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|1A|8|@]|9|@$R|1B|S|1C|1|1D]]|A|$]]|$1|T|3|-4|5|6|7|1E|8|@]|9|@]|A|$]]]|U|$V|$5|W|X|Y|A|$Z|10]]]]

The List is index based and new items will always be added to the end of the list. You can insert items at a certain index so the next items will move one position.
So yes, you can use it safely that way...
<blockquote>
The List(T) class is the generic
equivalent of the ArrayList class. It
implements the IList(T) generic
interface using an array whose size is
dynamically increased as required.
Elements in this collection can be
accessed using an integer index.
Indexes in this collection are
zero-based.
The List(T) is not guaranteed to be
sorted. You must sort the List(T)
before performing operations (such as
BinarySearch) that require the List(T)
to be sorted.
A List(T) can support multiple readers
concurrently, as long as the
collection is not modified.
Enumerating through a collection is
intrinsically not a thread-safe
procedure. In the rare case where an
enumeration contends with one or more
write accesses, the only way to ensure
thread safety is to lock the
collection during the entire
enumeration. To allow the collection
to be accessed by multiple threads for
reading and writing, you must
implement your own synchronization.
</blockquote>
You can read more about it on <a href="http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx" rel="noreferrer">MSDN</a>.

blocks|key|3133771|text|是的，List保证既有插入顺序也有检索顺序，这在MSDN上有说明(下面强调的是我的)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|BOLD|entityRanges|data|3133772|插入|3133773|+|3133774|3133775|将一个对象添加到+的端。|blockquote|3133776|3133777|3133778|Item参数为：|3133779|3133780|要添加到+的端的对象。|3133781|3133782|3133783|+|3133784|3133785|将指定集合的元素添加到+的端。|3133786|3133787|3133788|采集参数为：|3133789|3133790|应将其元素添加到+的端的集合。|3133791|3133792|3133793|检索|3133794|+|3133795|3133796|最初，枚举数位于集合中第一个元素之前。在此位置，Current是未定义的。因此，在读取的值之前，必须调用MoveNext将枚举数前进到集合的第一个元素Current。|3133797|3133798|3133799|在调用MoveNext之前，Current将返回相同的对象。MoveNext将Current设置为下一个元素。|3133800|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx|1|http://msdn.microsoft.com/en-us/library/3wcytfd1.aspx|2|http://msdn.microsoft.com/en-us/library/z883w3dc.aspx|3|http://msdn.microsoft.com/en-us/library/x854yt9s.aspx^0|3|4|9|C|3|4|0|0|0|0|1|1|0|0|A|2|0|0|0|0|8|0|0|0|4|6|5|0|0|0|0|1|2|0|0|0|B|D|2|0|0|0|0|6|0|0|0|8|A|5|0|0|0|0|2|0|0|1|3|0|0|0|2B|O|7|1G|8|23|7|0|0|0|0|1J|3|8|E|7|U|8|13|7|0^^$0|@$1|2|3|4|5|6|7|20|8|@$9|21|A|22|B|C]|$9|23|A|24|B|D]]|E|@$9|25|A|26|1|27]]|F|$]]|$1|G|3|H|5|6|7|28|8|@]|E|@]|F|$]]|$1|I|3|J|5|6|7|29|8|@]|E|@$9|2A|A|2B|1|2C]]|F|$]]|$1|K|3|-4|5|6|7|2D|8|@]|E|@]|F|$]]|$1|L|3|M|5|N|7|2E|8|@$9|2F|A|2G|B|D]]|E|@]|F|$]]|$1|O|3|-4|5|6|7|2H|8|@]|E|@]|F|$]]|$1|P|3|-4|5|6|7|2I|8|@]|E|@]|F|$]]|$1|Q|3|R|5|6|7|2J|8|@$9|2K|A|2L|B|D]]|E|@]|F|$]]|$1|S|3|-4|5|6|7|2M|8|@]|E|@]|F|$]]|$1|T|3|U|5|N|7|2N|8|@$9|2O|A|2P|B|D]|$9|2Q|A|2R|B|D]]|E|@]|F|$]]|$1|V|3|-4|5|6|7|2S|8|@]|E|@]|F|$]]|$1|W|3|-4|5|6|7|2T|8|@]|E|@]|F|$]]|$1|X|3|Y|5|6|7|2U|8|@]|E|@$9|2V|A|2W|1|2X]]|F|$]]|$1|Z|3|-4|5|6|7|2Y|8|@]|E|@]|F|$]]|$1|10|3|11|5|N|7|2Z|8|@$9|30|A|31|B|D]|$9|32|A|33|B|D]]|E|@]|F|$]]|$1|12|3|-4|5|6|7|34|8|@]|E|@]|F|$]]|$1|13|3|-4|5|6|7|35|8|@]|E|@]|F|$]]|$1|14|3|15|5|6|7|36|8|@$9|37|A|38|B|D]]|E|@]|F|$]]|$1|16|3|-4|5|6|7|39|8|@]|E|@]|F|$]]|$1|17|3|18|5|N|7|3A|8|@$9|3B|A|3C|B|D]|$9|3D|A|3E|B|D]]|E|@]|F|$]]|$1|19|3|-4|5|6|7|3F|8|@]|E|@]|F|$]]|$1|1A|3|-4|5|6|7|3G|8|@]|E|@]|F|$]]|$1|1B|3|1C|5|6|7|3H|8|@$9|3I|A|3J|B|D]]|E|@]|F|$]]|$1|1D|3|1E|5|6|7|3K|8|@]|E|@$9|3L|A|3M|1|3N]]|F|$]]|$1|1F|3|-4|5|6|7|3O|8|@]|E|@]|F|$]]|$1|1G|3|1H|5|N|7|3P|8|@$9|3Q|A|3R|B|D]|$9|3S|A|3T|B|C]|$9|3U|A|3V|B|C]|$9|3W|A|3X|B|C]]|E|@]|F|$]]|$1|1I|3|-4|5|6|7|3Y|8|@]|E|@]|F|$]]|$1|1J|3|-4|5|6|7|3Z|8|@]|E|@]|F|$]]|$1|1K|3|1L|5|6|7|40|8|@$9|41|A|42|B|D]|$9|43|A|44|B|C]|$9|45|A|46|B|C]|$9|47|A|48|B|C]|$9|49|A|4A|B|C]]|E|@]|F|$]]|$1|1M|3|-4|5|6|7|4B|8|@]|E|@]|F|$]]]|1N|$1O|$5|1P|1Q|1R|F|$1S|1T]]|1U|$5|1P|1Q|1R|F|$1S|1V]]|1W|$5|1P|1Q|1R|F|$1S|1X]]|1Y|$5|1P|1Q|1R|F|$1S|1Z]]]]

Yes, <a href="http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx" rel="noreferrer"><code>List&lt;T&gt;</code></a> guarantees both insertion order and retrieval order and this is documented on MSDN (emphasis below is mine).

<h2>Insertion</h2>

<a href="http://msdn.microsoft.com/en-us/library/3wcytfd1.aspx" rel="noreferrer"><code>List&lt;T&gt;.Add</code> Method</a>

<blockquote>
 Adds an object to the end of the <a href="http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx" rel="noreferrer"><code>List&lt;T&gt;</code></a>.
</blockquote>

Item parameter is:

<blockquote>
 The object to be added to the end of the <a href="http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx" rel="noreferrer"><code>List&lt;T&gt;</code></a>.
</blockquote>

<a href="http://msdn.microsoft.com/en-us/library/z883w3dc.aspx" rel="noreferrer"><code>List&lt;T&gt;.AddRange</code> Method</a>

<blockquote>
 Adds the elements of the specified collection to the end of the <a href="http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx" rel="noreferrer"><code>List&lt;T&gt;</code></a>.
</blockquote>

Collection parameter is:

<blockquote>
 The collection whose elements should be added to the end of the <a href="http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx" rel="noreferrer"><code>List&lt;T&gt;</code></a>.
</blockquote>

<h2>Retrieval</h2>

<a href="http://msdn.microsoft.com/en-us/library/x854yt9s.aspx" rel="noreferrer"><code>List&lt;T&gt;.Enumerator</code> Structure</a>

<blockquote>
 Initially, the enumerator is positioned before the first element in the collection. At this position, <code>Current</code> is undefined. Therefore, you must call <code>MoveNext</code> to advance the enumerator to the first element of the collection before reading the value of <code>Current</code>.
</blockquote>

<code>Current</code> returns the same object until <code>MoveNext</code> is called. <code>MoveNext</code> sets <code>Current</code> to the next element.

Does a <code>List&lt;T&gt;</code> always guarantee that items will be returned in the order they were added when enumerated?

Updated: Thanks for all the answers folks, puts my mind at ease. I had a quick poke around the <code>List&lt;T&gt;</code> class with .NET Reflector (should've probably done that in the first place) and indeed the underlying store is an array of <code>T</code> (<code>T[]</code>).

Does a List<T> guarantee that items will be returned in the order they were added?

List<T>是否总是保证项在枚举时按添加顺序返回？更新了：感谢大家的回答，让我放心了。我用.NET反射器快速浏览了一下List<T>类(可能一开始就应该这样做)，实际上底层存储是一个T (T[])数组。

问List<T>是否保证项目将按添加的顺序返回？
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