blocks|key|2772430|text|不要抛出System.Exception。永远不会。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2772431|它的问题在于调用代码。捕获一般的Exception对象是一种糟糕的做法，原因有很多。如果抛出Exception基类的一个实例，那么如果调用代码想要处理它，那么它们别无选择，只能捕获Exception。这迫使调用代码使用一种不好的做法。|2772432|此外，如果调用代码只得到Exception，那么它就没有可靠的方法来区分异常是什么。|2772433|通常最好使用一个预定义的例外(如果有)+(ArgumentException、InvalidOperationException等)。如果没有一个正确地描述了这种情况，那么自定义异常类是一种非常好的方法。|2772434|entityMap^0|4|G|0|G|9|1A|9|2I|9|0|C|9|0|L|H|13|P|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|J|3|K|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|L|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|M|$]]

Do not throw <code>System.Exception</code>. Ever.

The problem with it resides in the calling code. It is a bad practice to catch the general <code>Exception</code> object for many reasons. If you throw an instance of the <code>Exception</code> base class, then calling code has no choice but to catch <code>Exception</code> if they want to handle it. This forces the calling code to use a bad practice.

Also, the calling code has no reliable means of distinguishing what the exception was, if all it gets is <code>Exception</code>.

It is typically best to use one of the pre-defined exceptions if any are applicable (<code>ArgumentException</code>, <code>InvalidOperationException</code>, etc.). If none correctly describe the situation, then a custom exception class is a perfectly good way to go.

blocks|key|2772354|text|这是抛出异常本身的开销(创建对象、遍历堆栈等)。这是很昂贵的。创建你自己的异常类几乎不会增加任何开销，所以如果你要抛出一个异常，不要让它变成new+Exception("message")！|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2772355|entityMap^0|1Y|O|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

It's the overhead of throwing an exception itself (creating the object, walking the stack, etc.) that's costly. Making your own exception class adds almost no overhead, so if you're going to throw an exception, don't make it <code>new Exception("message")</code>!

blocks|key|869817|text|异常不是由人读取的(尽管它们的消息和堆栈跟踪是由人读取的)，它们是由代码读取的。如果你的代码可以做一些事情来响应一个自定义的异常，那么一定要去做。但是这个异常注定要被记录下来，没有必要自定义一个。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|869818|自定义异常的开销在于它们是另一件需要维护和测试的事情。如果现有的异常是合适的，请改用它。(例如，用ArgumentNullException代替ZipCodeNullException。)|offset|length|style|CODE|869819|entityMap^0|0|1D|L|20|K|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]|$D|N|E|O|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|P|8|@]|9|@]|A|$]]]|I|$]]

Exceptions aren't meant to be read by people (though their messages and stack traces are read by people), they're meant to be read by code. If there's something your code can do in response to a custom exception, by all means go for it. But the exception is just destined to be logged, there's no point to making a custom one.

The overhead of custom exceptions is that they're another thing to maintain and test. If an existing exception is suitable, use that instead. (E.g., <code>ArgumentNullException</code> instead of <code>ZipCodeNullException</code>.)

blocks|key|2486799|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2486800|如果有任何理由使您的异常以不同于标准异常的方式被捕获和处理，那么您应该创建自己的类。|ordered-list-item|2486801|如果您的异常有任何理由接受不同的参数(例如，根据您经常可能具有的一组参数生成特殊格式的消息)，那么您应该创建您自己的类。|2486802|2486803|在任何其他情况下，使用Exception都是安全的。一般来说，与标准异常相比，实例化或抛出自定义异常的成本并不高，至少与最初抛出异常的开销不同。根据定义，异常应该是异常的，因此抛出异常期间的性能不是问题。关键是，当您需要查看抛出异常的原因时，您需要所有的信息。|offset|length|style|CODE|2486804|entityMap^0|0|0|0|0|B|9|0^^$0|@$1|2|3|-4|4|5|6|O|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|P|7|@]|8|@]|9|$]]|$1|D|3|E|4|C|6|Q|7|@]|8|@]|9|$]]|$1|F|3|-4|4|5|6|R|7|@]|8|@]|9|$]]|$1|G|3|H|4|5|6|S|7|@$I|T|J|U|K|L]]|8|@]|9|$]]|$1|M|3|-4|4|5|6|V|7|@]|8|@]|9|$]]]|N|$]]

<ol>
<li>If there's any reason for your exception to be caught and handled differently from standard Exceptions, then you should create your own class.</li>
<li>If there's any reason for your exception to take different arguments (e.g. to produce a specially-formatted message based on a set of arguments that you're often likely to have), then you should create your own class.</li>
</ol>

In any other case, you're safe just using <code>Exception</code>. Generally speaking, it doesn't really cost any more to instantiate or throw a custom exception than a standard one, at least not compared with the expense of throwing an exception in the first place. Exceptions, by definition, should be exceptional, and therefore performance during the throwing of an exception is a non-issue. The point is to have all the information you need when the time comes to look at why that exception was thrown.

blocks|key|4562196|text|你的同事在胡说八道。不管类是什么，抛出异常的代价都是一样的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4562197|老实说，所有这些关于“昂贵”异常的说法-是的，它们比null检查或其他类似的异常更昂贵，所以永远不要将它们用作某些正常检查的替代品，但应该鼓励它们在有意义的地方使用(比如IOException，这是它们的一个很好的用例-+I/O问题是一个例外情况，它们通常必须在正常的程序流之外处理)。|4562198|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Your coworker is talking nonsense. Throwing an exception is the same cost regardless of the class.

And to be honest, all this talk of "expensive" exceptions - yes they are more expensive than a null check or some such, so don't ever use them as a replacement for some sanity check, but they should be encouraged where they make sense (like IOException for example, that's an excellent use case for them - problems with I/O are an exceptional case and they usually must be handled outside of normal program flow).

blocks|key|2772502|text|你永远不应该抛出System.Exception，因为只有通过catch(System.Exception)才能捕捉到。捕获这样的全面异常是非常糟糕的做法。您应该捕获特定的异常，这为您提供了一种在不使软件崩溃的情况下正确处理它的方法。通过生成自定义异常，您可以为自己提供一种潜在地识别它们并从中恢复的方法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2772503|例如，如果你的代码意味着打开一个文件，你得到一个未知的异常，你如何从它恢复？但是，如果您捕获到特定文件未找到异常，则恢复会容易得多。您可以明确地告诉用户该文件不存在。|2772504|我看不出有什么理由相信自定义异常比内置异常更昂贵。|2772505|entityMap^0|8|G|V|N|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|R|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|K|$]]

You should never throw a <code>System.Exception</code>, because then the only way to catch is is by <code>catch(System.Exception)</code>. It's very bad practice to catch a blanket exception like that. You should catch specific exceptions, which give you a way to properly handle it without crashing the software. By generating custom exceptions, you give yourself a way to potentially recognize and recover from them. 

For example, if your code means to open a file, and you get an unknown exception, how do you recover from it? However, if you catch a specific File Not Found exception, that is much easier to recover from. You can tell the user definitively that the file doesn't exist.

I don't see a reason to believe that custom exceptions are any more expensive than the built-in ones.

blocks|key|2772535|text|“昂贵”是一个相对的术语，正如名称所暗示的那样，异常应该是异常，所以它可能不会影响代码的性能。据我所知，抛出异常的成本与异常的类型无关，因此您不应该将自己限制在System.Exception。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2772536|但最重要的是：http://c2.com/cgi/wiki?PrematureOptimization|offset|length|2772537|entityMap|0|LINK|mutability|MUTABLE|url|http://c2.com/cgi/wiki?PrematureOptimization^0|0|7|18|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]]]]

"Expensive" is a relative term and - as the name already suggests - an exception should be an exception, so it will probably not affect the performance of your code. The cost of throwing an exception is - as far as I know - independent of the type of the exception, so you should not restrict yourself to System.Exception.

But most important: <a href="http://c2.com/cgi/wiki?PrematureOptimization" rel="nofollow">http://c2.com/cgi/wiki?PrematureOptimization</a>

blocks|key|869794|text|我更喜欢使用exception中最合适的构建，如果还不存在，可以从System.ApplicationException中派生出我自己的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|869795|我不推荐使用自定义消息抛出System.Exception。|869796|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

I prefer to use the most appropriate built in exception, and if that doesn't already exist, derive my own from System.ApplicationException.

I wouldn't recommend throwing System.Exception with a custom message.

I've read that throwing exceptions is an expensive operation. However, doesn't creating your own exceptions make your code more expressive and readable? 

Some of my coworkers suggest that you should just use System.Exception and insert your custom text into the message instead of creating a new custom exception.

I'm interested in other opinions. Appreciate any suggestions.

Cost of Custom Exceptions

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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我读到过抛出异常是一个开销很大的操作。但是，创建自己的异常难道不会使代码更具表现力和可读性吗？我的一些同事建议您只使用System.Exception并将自定义文本插入到消息中，而不是创建新的自定义异常。我对其他的观点很感兴趣。感谢您的建议。

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