我正在为一个朋友检查一些代码，并说他在try-finally块中使用了return语句。即使try块的其余部分没有触发，Finally部分中的代码仍然会触发吗?
例子:
public bool someMethod()
{
try
{
return true;
throw new Exception("test"); // doesn't seem to get executed
}
finally
{
//code in question
}
}
当前回答
有一个非常重要的例外，我在其他任何答案中都没有看到过，而且(在用c#编程了18年之后)我不敢相信我不知道。
如果你在catch块中抛出或触发任何类型的异常(不仅仅是奇怪的stackoverflowexception和类似的东西)，并且你没有在另一个try/catch块中包含整个try/catch/finally块，你的finally块将不会执行。这很容易证明-如果我没有自己看到它，考虑到我经常读到它只是非常奇怪的，微小的角落情况，可以导致finally块不执行，我不会相信它。
static void Main(string[] args)
{
Console.WriteLine("Beginning demo of how finally clause doesn't get executed");
try
{
Console.WriteLine("Inside try but before exception.");
throw new Exception("Exception #1");
}
catch (Exception ex)
{
Console.WriteLine($"Inside catch for the exception '{ex.Message}' (before throwing another exception).");
throw;
}
finally
{
Console.WriteLine("This never gets executed, and that seems very, very wrong.");
}
Console.WriteLine("This never gets executed, but I wasn't expecting it to.");
Console.ReadLine();
}
我相信这是有原因的，但奇怪的是，它并没有广为人知。(例如，这里提到了，但在这个特定的问题中没有提到。)
其他回答
这里有一个小测试:
class Class1
{
[STAThread]
static void Main(string[] args)
{
Console.WriteLine("before");
Console.WriteLine(test());
Console.WriteLine("after");
}
static string test()
{
try
{
return "return";
}
finally
{
Console.WriteLine("finally");
}
}
}
结果是:
before
finally
return
after
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.
}
引用自MSDN
Finally用于保证执行语句代码块，而不管前面的try块是如何退出的。
简单的回答:是的。
有一个非常重要的例外，我在其他任何答案中都没有看到过，而且(在用c#编程了18年之后)我不敢相信我不知道。
如果你在catch块中抛出或触发任何类型的异常(不仅仅是奇怪的stackoverflowexception和类似的东西)，并且你没有在另一个try/catch块中包含整个try/catch/finally块，你的finally块将不会执行。这很容易证明-如果我没有自己看到它，考虑到我经常读到它只是非常奇怪的，微小的角落情况，可以导致finally块不执行，我不会相信它。
static void Main(string[] args)
{
Console.WriteLine("Beginning demo of how finally clause doesn't get executed");
try
{
Console.WriteLine("Inside try but before exception.");
throw new Exception("Exception #1");
}
catch (Exception ex)
{
Console.WriteLine($"Inside catch for the exception '{ex.Message}' (before throwing another exception).");
throw;
}
finally
{
Console.WriteLine("This never gets executed, and that seems very, very wrong.");
}
Console.WriteLine("This never gets executed, but I wasn't expecting it to.");
Console.ReadLine();
}
我相信这是有原因的，但奇怪的是，它并没有广为人知。(例如，这里提到了，但在这个特定的问题中没有提到。)
