何时使用InvalidOperationException或NotSupportedException？ [英] When to use InvalidOperationException or NotSupportedException?

问题描述

我正在实现一个自定义集合实现，可以是只读的也可以是非只读的；也就是说，所有更改集合的方法都将调用一个在道德上等同于以下功能的函数：

I am implementing a custom collection implementation that can either be readonly or non-readonly; that is, all the methods that change the collection call a function that is the moral equivalent of:

private void ThrowIfReadOnly() {
    if (this.isReadOnly)
       throw new SomeException("Cannot modify a readonly collection.");
}

我不确定 NotSupportedException哪一个或 InvalidOperationException 在这种情况下应该使用。

I am not sure which of NotSupportedException or InvalidOperationException I should use in that case.

推荐答案

MSDN仅在 NotSupportedException ：

The MSDN only has one bit of guidance on this precise topic, on NotSupportedException:

对于某些情况下有时对象可能执行请求的操作，并且对象状态确定是否可以执行该操作，请参见 InvalidOperationException 。

以下内容纯属我自己的解释的规则：

What follows is purely my own interpretation of the rule:

• 如果对象的状态可以更改，则操作在对象的'期间可以变为无效/有效的生存期，则应使用 InvalidOperationException 。


• 如果操作在整个对象的生存期内始终是无效/有效的，则 NotSupportedException 。


• 在这种情况下，生命周期的意思是任何人都可以引用该对象的整个时间-也就是说，即使在 Dispose（）调用之后，通常也会使大多数其他实例方法不可用；
  
  
  
  
  • 如Martin Liversage所指出的那样，在对象被处置的情况下，更具体的 ObjectDisposedException 应该使用type。 （这仍然是 InvalidOperationException 的子类型。）
  
  
  • If the object's state can change so that the operation can become invalid / valid during the object's lifetime, then InvalidOperationException should be used.
  • If the operation is always invalid / valid during the whole object's lifetime, then NotSupportedException should be used.
  • In that case, "lifetime" means "the whole time that anyone can get a reference to the object" - that is, even after a Dispose() call that often makes most other instance methods unusable;
    • As pointed out by Martin Liversage, in the case of an object having been disposed, the more specific ObjectDisposedException type should be used. (That is still a subtype of InvalidOperationException).

    在这种情况下，这些规则的实际应用如下：

    The practical application of these rules in that case would be as follows:

    
    
    • 如果 isReadOnly 只能在创建对象时设置（例如，构造函数参数），而不能在任何其他时间设置，然后 NotSupportedException 应该使用。
    
    
    • 如果 isReadOnly 在对象的生存期内可以更改，则 InvalidOperationException 应该被使用。
      
      
      
      
      • 但是， InvalidOperationException 与 NotSupportedException 实际上是没有意义的-给定 <$ MSDN上的c $ c> IsReadOnly ， IsReadOnly 唯一允许的行为是，初始化集合后其值永远不会更改。这意味着一个collection实例可以是可修改的也可以是只读的-但它应该在初始化时选择一个实例，并在整个生命周期中坚持使用它。
      
      
      • If isReadOnly can only be set at the time when the object is created (e.g. a constructor argument), and never at any other time, then NotSupportedException should be used.
      • If isReadOnly can change during the lifetime of the object, then InvalidOperationException should be used.
        • However, the point of InvalidOperationException vs NotSupportedException is actually moot in the case of implementing a collection - given the description of IsReadOnly on MSDN, the only permitted behavior for IsReadOnly is that its value never changes after the collection is initialized. Meaning that a collection instance can either be modifiable or read-only - but it should choose one at initialization and stick with it for the rest of its lifetime.

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