通常是的,最终会运行。
对于以下三种情况,finally将始终运行:
No exceptions occur
Synchronous exceptions (exceptions that occur in normal program flow).
This includes CLS compliant exceptions that derive from System.Exception and non-CLS compliant exceptions, which do not derive from System.Exception. Non-CLS compliant exceptions are automatically wrapped by the RuntimeWrappedException. C# cannot throw non-CLS complaint exceptions, but languages such as C++ can. C# could be calling into code written in a language that can throw non-CLS compliant exceptions.
Asynchronous ThreadAbortException
As of .NET 2.0, a ThreadAbortException will no longer prevent a finally from running. ThreadAbortException is now hoisted to before or after the finally. The finally will always run and will not be interrupted by a thread abort, so long as the try was actually entered before the thread abort occurred.
下面的场景,最后将不会运行:
Asynchronous StackOverflowException.
As of .NET 2.0 a stack overflow will cause the process to terminate. The finally will not be run, unless a further constraint is applied to make the finally a CER (Constrained Execution Region). CERs should not be used in general user code. They should only be used where it is critical that clean-up code always run -- after all the process is shutting down on stack overflow anyway and all managed objects will therefore be cleaned-up by default. Thus, the only place a CER should be relevant is for resources that are allocated outside of the process, e.g., unmanaged handles.
通常,非托管代码在被用户代码使用之前由某个托管类包装。托管包装器类通常会使用SafeHandle来包装非托管句柄。SafeHandle实现了一个关键的终结器和一个在CER中运行的Release方法,以保证清理代码的执行。出于这个原因,您不应该看到cer遍布整个用户代码。
因此,finally不运行在StackOverflowException上的事实应该对用户代码没有影响,因为进程无论如何都会终止。如果你有一些边缘情况,你确实需要清理一些非托管资源,在SafeHandle或CriticalFinalizerObject之外,然后使用CER如下所示;但请注意,这是一种糟糕的做法——非托管概念应该通过设计抽象为托管类和适当的安全句柄。
例如,
// No code can appear after this line, before the try
RuntimeHelpers.PrepareConstrainedRegions();
try
{
// This is *NOT* a CER
}
finally
{
// This is a CER; guaranteed to run, if the try was entered,
// even if a StackOverflowException occurs.
}