.Net4, Monitor.Enter(lockObject, acquiredLock)

Question

在 .Net4 中，Monitor.Enter(Object)被标记为过时:

[ObsoleteAttribute("This method does not allow its caller to reliably release the lock.  Please use an overload with a lockTaken argument instead.")]
public static void Enter(
    Object obj
)

还有一个新方法Monitor.Enter(lockObject, acquiredLock)使用这种用法:

bool acquiredLock = false;

try
{
    Monitor.Enter(lockObject, ref acquiredLock);

    // Code that accesses resources that are protected by the lock.

}
finally
{
    if (acquiredLock)
    {
        Monitor.Exit(lockObject);
    }
}

我以前是这样做的:

Monitor.Enter(lockObject);
try
{

    // Code that accesses resources that are protected by the lock.
}
finally
{
    Monitor.Exit(lockObject);
}

错了吗？为什么 ？也许在输入之后但在尝试之前有一个中断？
正如 Eamon Nerbonne 所问:如果在 monitor.exit 之前的 finally 中出现异步异常会怎样？

答案:ThreadAbortException

When this exception is raised, the runtime executes all the finally blocks before ending the thread.

Answer 1

正如您在问题末尾所建议的那样，问题是 asynchronous exception可以在调用 Monitor.Enter 之后但在您输入 try block 之前抛出。

新的处理方式确保无论发生什么情况，您都将到达 finally block 并能够释放锁定如果您获得了它。 (例如，如果 Monitor.Enter 抛出异常，您可能无法获取它。)

IIRC，这是针对 .NET 4.0 时 lock 关键字的新行为。