问题描述
在我的应用程序需要的，如果一个特定类的属性为null或空抛出异常（如果它是一个字符串）。我不知道什么是在这种情况下，用最好的例外。我不想创建一个新的异常，我不知道ArgumentNullException为宜在这种情况下。
我应该创建一个新的异常或有例外，我可以使用吗？
我不介意抛出ApplicationException。
有关标准异常的 MSDN指南规定：
此外，对于物业的设计 MSDN指南说：
于是抛出 ArgumentNullException 在空的制定者，而的ArgumentException 的空字符串，什么事都不做，在吸气。由于二传罚球，只有你可以访问支持字段，它很容易，以确保它不包含无效值。具有吸气掷然后毫无意义。然而，这可能是一个好去处使用<$c$c>Debug.Assert.
如果你真的不能提供适当的默认的话，我想你有三种选择：
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刚返回无论是在性能和文档这种行为作为使用合同的一部分。让来电处理。您可能还需要在构造一个有效的价值。这可能是完全不恰当的，虽然您的应用程序。
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替换财产的方法：当传递一个无效的值，它抛出一个setter方法，并抛出一个getter方法
InvalidOperationException异常当地产从未分配有效值。 -
投掷
InvalidOperationException异常从吸气，你可以考虑财产从来没有被赋予无效状态。虽然你不应该从正常干将扔，我想这可能是一个很好的理由，使一个例外。
如果您选择选项2或3，您还应该包括TryGet-方法，该方法返回一个布尔这表明如果属性被设置为一个有效的值，如果是返回一个的值超出参数。否则，你强制来电者是ppared处理$ P $的 InvalidOperationException异常，除非他们有previously设置属性本身，从而知道它会不会抛出。比较 int.Parse 与 int.TryParse 。
我建议使用选项2的TryGet方法。它没有违反任何准则，并规定了调用code的最低要求。
关于其他建议 ApplicationException的是太一般。 的ArgumentException 是有点太笼统了空，但罚款，否则。 MSDN文档一次：
事实上，你不应该使用 ApplicationException的在所有（的）：
出现InvalidOperationException 意图不是时的参数的方法或属性是无效的，但因为当操作的作为一个整体是无效的（ 文档）。它不应该被从设定器抛出：
顺便说一句， InvalidOperationException异常是当操作是无效的为对象的当前状态。的如果操作始终是整个类无效，你应该使用<$c$c>NotSupportedException.
In my application I need to throw an exception if a property of a specific class is null or empty (in case it's a string). I'm not sure what is the best exception to use in this case. I would hate to create a new exception and I'm not sure if ArgumentNullException is appropriate in this case.
Should I create a new exception or there's an exception I can use?
I don't mind to throw an ApplicationException.
The MSDN guidelines for standard exceptions states:
Additionally, the MSDN guidelines for property design say:
So throw ArgumentNullException in the setter on null, and ArgumentException on the empty string, and do nothing in the getter. Since the setter throws and only you have access to the backing field, it's easy to make sure it won't contain an invalid value. Having the getter throw is then pointless. This might however be a good spot to use Debug.Assert.
If you really can't provide an appropriate default, then I suppose you have three options:
Just return whatever is in the property and document this behaviour as part of the usage contract. Let the caller deal with it. You might also demand a valid value in the constructor. This might be completely inappropriate for your application though.
Replace the property by methods: A setter method that throws when passed an invalid value, and a getter method that throws
InvalidOperationExceptionwhen the property was never assigned a valid value.Throw
InvalidOperationExceptionfrom the getter, as you could consider 'property has never been assigned' an invalid state. While you shouldn't normally throw from getters, I suppose this might be a good reason to make an exception.
If you choose options 2 or 3, you should also include a TryGet- method that returns a bool which indicates if the property has been set to a valid value, and if so returns that value in an out parameter. Otherwise you force callers to be prepared to handle an InvalidOperationException, unless they have previously set the property themselves and thus know it won't throw. Compare int.Parse versus int.TryParse.
I'd suggest using option 2 with the TryGet method. It doesn't violate any guidelines and imposes minimal requirements on the calling code.
About the other suggestionsApplicationException is way too general. ArgumentException is a bit too general for null, but fine otherwise. MSDN docs again:
In fact you shouldn't use ApplicationException at all (docs):
InvalidOperationException is intended not for when the arguments to a method or property are invalid, but for when the operation as a whole is invalid (docs). It should not be thrown from the setter:
Incidentally, InvalidOperationException is for when the operation is invalid for the object's current state. If the operation is always invalid for the entire class, you should use NotSupportedException.
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