c#Thread.Abort()和Thread.ResetAbort()的使用

c# Thread.Abort()和Thread.ResetAbort()的使用

Thread类的Abort()方法用于终止正在运行的线程&＃xff08;.net core中Abort()方法虽然存在&＃xff0c;但是调用它会引发PlatformNotSupportedException的异常提示&＃xff09;。它可以强行终止线程&＃xff0c;而不管线程是否是sleep中。
执行了Abort()后&＃xff0c;被终止的线程就会继续运行catch{}finally{}块中代码&＃xff0c;因为是强行终止&＃xff0c;catch块之后的语句则不再运行。除非在catch语句中执行Thread.ResetAbort()这个静态方法。
先举例没有ResetAbort()的情况:

using System;
using System.Threading;class Test
{public static void Main(){Thread newThread &＃61; new Thread(new ThreadStart(TestMethod));newThread.Start();Thread.Sleep(1000);// Abort newThread.Console.WriteLine("Main aborting new thread.");newThread.Abort("Information from Main.");// Wait for the thread to terminate.newThread.Join();Console.WriteLine("New thread terminated - Main exiting.");}static void TestMethod(){try{while (true){Console.WriteLine("New thread running.");Thread.Sleep(1000);}}catch (ThreadAbortException abortException){Console.WriteLine((string)abortException.ExceptionState);}finally{Console.WriteLine("Do somthing else in funally{}.");}Console.WriteLine("Do somthing else here.");}
}
/*输出结果:
New thread running.
Main aborting new thread.
Information from Main.
Do somthing else in funally{}.
New thread terminated - Main exiting.
*/


看输出结果&＃xff0c;可以看到线程被Abort之后&＃xff0c;执行catch和finally块中的内容&＃xff0c;但是不会执行finally块之后的内容。
再看增加ResetAbort()的代码&＃xff1a;

using System;
using System.Threading;class Test
{public static void Main(){Thread newThread &＃61; new Thread(new ThreadStart(TestMethod));newThread.Start();Thread.Sleep(1000);// Abort newThread.Console.WriteLine("Main aborting new thread.");newThread.Abort("Information from Main.");// Wait for the thread to terminate.newThread.Join();Console.WriteLine("New thread terminated - Main exiting.");}static void TestMethod(){try{while (true){Console.WriteLine("New thread running.");Thread.Sleep(1000);}}catch (ThreadAbortException abortException){Console.WriteLine((string)abortException.ExceptionState);Thread.ResetAbort();}finally{Console.WriteLine("Do somthing else in funally{}.");}Console.WriteLine("Do somthing else here.");}
}
/*输出结果:
New thread running.
Main aborting new thread.
Information from Main.
Do somthing else in funally{}.
Do somthing else here.
New thread terminated - Main exiting.
*/


从结果中可以看到&＃xff0c;线程被终止了&＃xff0c;由于执行了Thread.ResetAbort()&＃xff0c;因此就允许继续执行finally块之后的代码。
注意: 如果Thread.ResetAbort()语句放在catch块中&＃xff0c;最好应当把Thread.ResetAbort()语句放在catch{}代码块最后&＃xff0c;否则会把abortException.ExceptionState中的内容给清空了。Thread.ResetAbort()还可以放在finally块中&＃xff0c;它同样也可以允许继续执行finally块之后的代码。另外&＃xff0c;Thread.ResetAbort()只能执行一次&＃xff0c;不能执行二次及以上&＃xff0c;否则会出新的异常。

现在解释一下&＃xff0c;在默认&＃xff08;不调用Thread.ResetAbort()&＃xff09;的情况下&＃xff0c; finally块后的代码是执行不到的&＃xff0c;这是由于 ThreadAbortException这个异常非常特殊&＃xff0c;它会在finally块的最后&＃xff08;如果没有finally块&＃xff0c;则是在catch块的最后&＃xff09;重新扔出一个 ThreadAbortException异常。(不过这个异常在外部抓不到&＃xff0c;它仅仅是为了退出线程用的)。