Question

所有我已经搜索了这个问题，我找到了很多答案并不难找到我的问题的解决方案。但是，我有奇怪的经历，我不知道这就是为什么我要求别人给我一些建议的原因。这是我的代码：

    void SetThread()
    {
        for (int i = 0; i < _intArrayLength; i++)
        {
            Console.Write(string.Format("SetThread->i: {0}\r\n", i));
            _th[i] = new Thread(new ThreadStart(() => RunThread(i)));
            _th[i].Start();
        }
    }

    void RunThread(int num)
    {
        Console.Write(string.Format("RunThread->num: {0}\r\n", num));
    }

是的，它们是普通的线程代码。我希望所有的线程数组都应该调用RunThread方法10次。它应该像

SetThread->i: 0
SetThread->i: 1
SetThread->i: 2
SetThread->i: 3
SetThread->i: 4
SetThread->i: 5
SetThread->i: 6
SetThread->i: 7
SetThread->i: 8
SetThread->i: 9
RunThread->num: 0
RunThread->num: 1
RunThread->num: 2
RunThread->num: 3
RunThread->num: 4
RunThread->num: 5
RunThread->num: 6
RunThread->num: 7
RunThread->num: 8
RunThread->num: 9

这是我期望的。订单并不重要。但我得到的结果如下。

SetThread->i: 0
SetThread->i: 1
SetThread->i: 2
The thread '<No Name>' (0x18e4) has exited with code 0 (0x0).
The thread '<No Name>' (0x11ac) has exited with code 0 (0x0).
The thread '<No Name>' (0x1190) has exited with code 0 (0x0).
The thread '<No Name>' (0x1708) has exited with code 0 (0x0).
The thread '<No Name>' (0xc94) has exited with code 0 (0x0).
The thread '<No Name>' (0xdac) has exited with code 0 (0x0).
The thread '<No Name>' (0x12d8) has exited with code 0 (0x0).
The thread '<No Name>' (0x1574) has exited with code 0 (0x0).
The thread '<No Name>' (0x1138) has exited with code 0 (0x0).
The thread '<No Name>' (0xef0) has exited with code 0 (0x0).
SetThread->i: 3
RunThread->num: 3
RunThread->num: 3
RunThread->num: 3
SetThread->i: 4
RunThread->num: 4
SetThread->i: 5
SetThread->i: 6
RunThread->num: 6
RunThread->num: 6
SetThread->i: 7
RunThread->num: 7
SetThread->i: 8
RunThread->num: 8
SetThread->i: 9
RunThread->num: 9
RunThread->num: 10

我期望RunThread函数应该携带从0到9的参数（num）。我无法弄清楚错误信息是什么。 “线程''~~等等。有人能给我一些线索吗？

Answer 1

你是creating a closure over the loop variable - 一个简单的解决方法就是创建一个本地副本，这样你的主题就会使用所需的值：

void SetThread()
    {
        for (int i = 0; i < _intArrayLength; i++)
        {
           int currentValue = i;
            Console.Write(string.Format("SetThread->i: {0}\r\n", i));
            _th[i] = new Thread(() => RunThread(currentValue));
            _th[i].Start();
        }
    }

Answer 2

您可能希望更改此类代码以使用ParameterizedThreadStart委托：

    for (int i = 0; i < _intArrayLength; i++)
    {
        Console.Write(string.Format("SetThread->i: {0}\r\n", i));
        _th[i] = new Thread((a) => RunThread((int)a));
        _th[i].Start(i);
    }

否则，从您的线程入口点委托() => RunThread(i)您正在从父主线程的上下文访问变量i，这可能会在您的新线程开始之前发生变化。

如何在C＃中将参数传递给线程

2 个答案: