c# - 尝试锁定对象时尝试/捕获

Question

我是多线程的新手。当对象被另一个线程锁定时，我试图锁定对象，我预计会出现错误并尝试使用 Exception，但它没有用。

class Program
    {
        static readonly object lockNum = new object();
        static int A = 10;

        public static void Thread1()
        {
            lock (lockNum)
            {
                A = 100;
                Console.WriteLine(A);
            }
        }

        public static void Thread2()
        {
            Thread.Sleep(1000);
            lock (lockNum)
            {
                Thread.Sleep(9000);
                Console.WriteLine(A);
                Console.WriteLine("Thread 2 is executed");
            }
        }

        public static void Thread3()
        {
            Thread.Sleep(3000);

            try
            {
                lock (lockNum)
                {
                    Console.WriteLine(A);
                    Console.WriteLine("Thread 3 is executed");
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine("Object is locked");
            }

        }

    }

    public class MyClass
    {

        public static void Main()
        {
            Thread tid1 = new Thread(new ThreadStart(Program.Thread1));
            Thread tid2 = new Thread(new ThreadStart(Program.Thread2));
            Thread tid3 = new Thread(new ThreadStart(Program.Thread3));

            tid1.Start();
            tid2.Start();
            tid3.Start();

            Console.ReadLine();
        }
    }

Thread2 和 Thread3 在 Thread.Sleep(9000); 之后一起运行，我预计 3 秒后会出现异常，因为该对象仍被 Thread2 锁定。我试图让 Thread3 再次 sleep 3 秒以检查对象是否已解锁(可能是 WriteLine 错误)并重复直到对象被解锁。

Answer 1

锁不会抛出异常，它们只是等待其他线程释放锁。

如果您想在无法领取锁时跳过代码，您可以使用

if (Monitor.TryEnter(lockNum))
{
    Console.WriteLine("No one else had the lock, now it's mine!");
}
else
{
    Console.WriteLine("Another thread won :(");
}

您可以选择为该方法提供超时。