c# - 检测线程已在 C# .net 中运行？

Question

我正在使用以下代码。

public void runThread(){
    if (System.Diagnostics.Process.GetProcessesByName("myThread").Length == 0)
    {
    Thread t = new Thread(new ThreadStart(go));
    t.IsBackground = true;
    t.Name = "myThread";
    t.Start();
    }
    else
    {
      System.Diagnostics.Debug.WriteLine("myThreadis already Running.");
    }   
}
public void go()
{
    //My work goes here
}

我多次调用 runThread() 函数，但我希望线程仅在线程未运行时启动。怎么可能？

Answer 1

GetProcessesByName 不会在您的应用程序中查找线程，而是在您的机器中查找进程。事实上，在您自己的应用程序中没有很好的方法来查询线程(一个问题是编写调试器)。

对于你想要的，你可以创建一个 wrapper class for your threads这样您就可以查询它们是否正在运行。或者 keep track of the threads yourself by other means .

您也可以考虑使用 Lazy<Thread>需要时会初始化的字段，可以查询线程是否存活。 测试后Lazy<Thread>这不是一个好主意。

---

源自 Simon's answer :

private int running;

public void runThread()
{
    if (Interlocked.CompareExchange(ref running, 1, 0) == 0)
    {
        Thread t = new Thread
        (
            () =>
            {
                try
                {
                    go();
                }
                catch
                {
                    //Without the catch any exceptions will be unhandled
                    //(Maybe that's what you want, maybe not*)
                }
                finally
                {
                    //Regardless of exceptions, we need this to happen:
                    running = 0;
                }
            }
        );
        t.IsBackground = true;
        t.Name = "myThread";
        t.Start();
    }
    else
    {
        System.Diagnostics.Debug.WriteLine("myThreadis already Running.");
    }   
}

public void go()
{
    //My work goes here
}

*: Gotta catch'em all

---

Wajid和 Segey是对的。您可以只拥有一个 Thread 字段。请允许我举个例子:

private Thread _thread;

public void runThread()
{
    var thread = _thread;
    //Prevent optimization from not using the local variable
    Thread.MemoryBarrier();
    if
    (
        thread == null ||
        thread.ThreadState == System.Threading.ThreadState.Stopped
    )
    {
        var newThread = new Thread(go);
        newThread.IsBackground = true;
        newThread.Name = "myThread";
        newThread.Start();
        //Prevent optimization from setting the field before calling Start
        Thread.MemoryBarrier();
        _thread = newThread;
    }
    else
    {
        System.Diagnostics.Debug.WriteLine("myThreadis already Running.");
    }
}

public void go()
{
    //My work goes here
}

注意:最好使用第一个备选方案(源自 Simon 的回答)，因为它是线程安全的。也就是说，如果有多个线程同时调用 runThread 方法，则不会有创建多个线程的风险。