blocks|key|2165624|text|您应该查看值类型使用指南：http://msdn.microsoft.com/en-us/library/y23b5415(vs.71).aspx|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2165625|这篇文章列举了几个要点，但我认为最有价值的几点如下|2165626|价值是不变的吗？|unordered-list-item|2165627|是否希望类型具有值语义？|2165628|如果这两个问题的答案都是肯定的，那么您几乎肯定希望使用一个结构。否则我建议你去上课。|2165629|使用大量成员的结构存在问题。但我发现，如果我考虑以上两点，在我的价值类型中，我很少有超过建议的成员数目/大小。|2165630|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/y23b5415(vs.71).aspx^0|D|1O|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|6|7|10|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|11|8|@]|9|@]|C|$]]|$1|I|3|J|5|H|7|12|8|@]|9|@]|C|$]]|$1|K|3|L|5|6|7|13|8|@]|9|@]|C|$]]|$1|M|3|N|5|6|7|14|8|@]|9|@]|C|$]]|$1|O|3|-4|5|6|7|15|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]]]

You should check out the value type usage guidelines: <a href="http://msdn.microsoft.com/en-us/library/y23b5415(vs.71).aspx" rel="noreferrer">http://msdn.microsoft.com/en-us/library/y23b5415(vs.71).aspx</a>

The article lists several important points but the few that I feel are the most valuable are the following

<ul>
<li>Is the value immutable?</li>
<li>Do you want the type to have value semantics?</li>
</ul>

If the answer to both questions is yes then you almost certainly want to use a Structure. Otherwise I would advise going with a class. 

There are issues with using structures with a large amount of members. But I find that if I consider the two points above, rarely do I have more than the recommended number of members / size in my value types.

blocks|key|851864|text|MSDN有一个很好的准则文件来涵盖结构的使用。概括地说：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|851865|表现得像原始类型。|unordered-list-item|851866|实例大小小于16字节。|851867|是不可改变的。|851868|价值语义是可取的。|851869|否则，使用类。|851870|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/y23b5415(vs.71).aspx^0|A|4|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|C|$]]|$1|G|3|H|5|F|7|11|8|@]|9|@]|C|$]]|$1|I|3|J|5|F|7|12|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|13|8|@]|9|@]|C|$]]|$1|M|3|N|5|6|7|14|8|@]|9|@]|C|$]]|$1|O|3|-4|5|6|7|15|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]]]

MSDN has a good <a href="http://msdn.microsoft.com/en-us/library/y23b5415(vs.71).aspx" rel="nofollow noreferrer">guidelines document</a> to cover structure usage. To summarize:

<ul>
<li>Act like primitive types.</li>
<li>Have an instance size under 16 bytes.</li>
<li>Are immutable.</li>
<li>Value semantics are desirable.</li>
</ul>

Otherwise, use a class.

blocks|key|635337|text|您应该始终使用Class作为首选，仅出于非常具体的原因(正如其他人已经概述的那样)才更改为Structure。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|635338|根据“在这个类中只需要它”的程度，您可以通过使用匿名类型完全避免嵌套类型；这只能在单个方法中工作：|BOLD|635339|Public+Class+Foo
++++Public+Sub+Bar
++++++++Dim+baz+=+New+With+{+.Str+=+"String",+.I+=+314+}
++++End+Sub
End+Class|code-block|syntax|javascript|635340|您不能(很容易地-您可以用泛型做一些事情)以类型错误的方式将实例baz移出Sub之外。当然，Object可以保存任何东西，甚至是匿名类型的实例。|635341|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/bb384767.aspx^0|7|5|19|9|0|15|2|O|4|0|0|0|W|3|11|3|1A|6|0^^$0|@$1|2|3|4|5|6|7|X|8|@$9|Y|A|Z|B|C]|$9|10|A|11|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|12|8|@$9|13|A|14|B|H]]|D|@$9|15|A|16|1|17]]|E|$]]|$1|I|3|J|5|K|7|18|8|@]|D|@]|E|$L|M]]|$1|N|3|O|5|6|7|19|8|@$9|1A|A|1B|B|C]|$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]]|D|@]|E|$]]|$1|P|3|-4|5|6|7|1G|8|@]|D|@]|E|$]]]|Q|$R|$5|S|T|U|E|$V|W]]]]

You should always use a <code>Class</code> as your first choice, changing to <code>Structure</code> only for very specific reasons (as others have already outlined).

Depending on how much you "only need it in this class", you might be able to avoid the nested type completely by using an <a href="http://msdn.microsoft.com/en-us/library/bb384767.aspx" rel="nofollow noreferrer">anonymous type</a>; this will only work within a single method:

<pre><code>Public Class Foo
 Public Sub Bar
 Dim baz = New With { .Str = "String", .I = 314 }
 End Sub
End Class
</code></pre>

you can't (readily--there are a few things you can do with generics) move the instance <code>baz</code> outside of the <code>Sub</code> in a typesafe manner. Of course an <code>Object</code> can hold anything, even an instance of an anonymous type.

blocks|key|635378|text|如果您需要复制对象，或者不希望通过传递的函数修改对象，我认为结构是很好的。由于传递的函数不能修改原来传递的结构，而是得到了它的新副本，这可以成为生命保护程序。(除非它们明显地作为ByRef传递)，并且可以为您省去.NET中的严重复制疯狂或实现ICloneSomething实现的痛苦。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|635379|但总体思路是以更语义的方式定义自定义数据结构。|635380|关于迁移到类，如果要迁移到类的一部分，通常这是一个很好的实践，因为您的结构与与名称空间无关的类相关的时间是99%25。|635381|如果要将其转换为类，则需要考虑“它是否定义了数据结构”和“它是否很昂贵？”因为它会被复制到整个地方，“你想被过路人的修改所影响吗？”|635382|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|L|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|M|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

I think structures are great if you need copy the object or do not want it to be modified by the passed function. Since passed functions can not modify the originally passed structure instead got a new copy of it, this can be a life saver. (unless they passed as ByRef obviously) and can save you trouble of deep copy craziness in .NET or implementing pain of an ICloneSomething implementation.

But the general idea is defining a custom data structure in a more semantic way.

About moving to a class, if you are moving into a class where it'll be part of a class, generally this is good practice since your structure is 99% of the time related with one of you classes not related with a namespace.

If you are converting it to a class then you need to consider "is it defining a data strcuture" and "is it expensive?" since it's gonna be copied all over the place, "do you want to get affected by modifications done by the passers?"

blocks|key|851906|text|Marc和Rex引用的使用指南非常好，很好地涵盖了您不确定想要哪一个的情况。我将列出一些需要使用结构的用例。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|851907|当您需要设置内存中字段的布局时|unordered-list-item|851908|与非托管代码的互操作。|851909|当你想做工会的时候。|offset|length|851910|851911|​|851912|你需要一个内联的固定大小缓冲器。|851913|您希望能够在相对安全的情况下执行相当于reinterpret_cast的操作(只要结构不包含任何本身是引用类型的字段。|851914|这些通常是边缘情况，并且(互操作除外)不推荐实践，除非它们的使用是项目/程序成功所必需的。|851915|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/acxa5b99.aspx|1|http://msdn.microsoft.com/en-us/library/zycewsya.aspx^0|0|1|1|4|2|0|1|0|0|8|7|1|0|0|0^^$0|@$1|2|3|4|5|6|7|13|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|14|8|@]|9|@]|A|$]]|$1|E|3|F|5|D|7|15|8|@]|9|@]|A|$]]|$1|G|3|H|5|D|7|16|8|@]|9|@$I|17|J|18|1|19]]|A|$]]|$1|K|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|1B|8|@]|9|@]|A|$]]|$1|N|3|O|5|D|7|1C|8|@]|9|@$I|1D|J|1E|1|1F]]|A|$]]|$1|P|3|Q|5|D|7|1G|8|@]|9|@]|A|$]]|$1|R|3|S|5|6|7|1H|8|@]|9|@]|A|$]]|$1|T|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]]|U|$V|$5|W|X|Y|A|$Z|10]]|11|$5|W|X|Y|A|$Z|12]]]]

The usage guidelines referenced by Marc and Rex are excellent and nicely cover cases where you aren't sure which one you would want. I will list some use cases where use of a struct is a requirement.

<ul>
<li>When you need to set the layout of the fields in memory

<ul>
<li>Interop with unmanaged code.</li>
<li>When you want to make <a href="http://msdn.microsoft.com/en-us/library/acxa5b99.aspx" rel="nofollow noreferrer">Unions</a>.</li>
</ul></li>
<li>You need a <a href="http://msdn.microsoft.com/en-us/library/zycewsya.aspx" rel="nofollow noreferrer">fixed size buffer</a> inlined.</li>
<li>You want to be able to do the equivalent of a reinterpret_cast with relative safety (so long as the struct does not contain any fields which are themselves reference types.</li>
</ul>

These are normally edge cases and (with the exception of interop) not recommended practices unless their use is necessary for the success of the project/program.

In a recent project I was working I created a structure in my class to solve a problem I was having, as a colleague was looking over my shoulder he looked derisively at the structure and said "move it into a class". 

I didn't have any argument for not moving it into a class other than I only need it in this class but this kind of falls down because couldn't I make it a nested class? 

When is it ok to use a structure?

when is it ok to use a structure rather than a class

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在我最近做的一个项目中，我在班上创建了一个结构来解决我遇到的一个问题。当一个同事回头看我的时候，他嘲笑地看着这个结构，说“把它变成一个类”。除了我的之外，我没有任何理由不将它移到其他类中，只有在这个类中需要它，但是这种类型的下降是因为我不能使它成为一个嵌套类吗？什么时候可以使用结构？

问什么时候可以使用结构而不是类？
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问什么时候可以使用结构而不是类？
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