正在更改的线程参数 [英] Thread parameters being changed

问题描述

启动多线程时，我解析的id参数有时是错误的.这是我的启动:

When starting multiple threads, the id parameter I'm parsing is sometimes wrong. Here is my startup:

for (int i = 0; i < _threadCount; i++)
{
    Thread thread = new Thread(() => WorkerThread(i));
    thread.Start();
    _threads.Add(thread);
}

还有我的线程函数:

private void WorkerThread(int id)
{
    Console.WriteLine("[{0}] Thread started {1}", DateTime.Now.ToLongTimeString(), id);
}

这段代码的输出是:

[19:10:54] Thread start 3
[19:10:54] Thread start 9
[19:10:54] Thread start 4
[19:10:54] Thread start 12
[19:10:54] Thread start 11
[19:10:54] Thread start 3
[19:10:54] Thread start 12
[19:10:54] Thread start 6
[19:10:54] Thread start 9
[19:10:54] Thread start 6
[19:10:54] Thread start 13
[19:10:54] Thread start 2
[19:10:54] Thread start 15
[19:10:54] Thread start 9
[19:10:54] Thread start 15

在我看来，这段代码应该使用唯一的 id 创建每个线程，而不是像上面看到的那样重复.

Where in my mind, this code should create every thread with a unique id instead of duplicates as seen above.

编译器信息:

平台目标:x64

目标框架:.NET Framework 4.5

Target Framework: .NET Framework 4.5

推荐答案

你应该小心在启动线程后不小心修改了像 i 这样捕获的变量，因为 i共享.i 变量在整个循环的生命周期中引用相同的内存位置.解决方案是使用一个临时变量，如下所示:

You should be careful about accidentally modifying captured variables like i after starting the thread, because the i is shared. The i variable refers to the same memory location throughout the loop’s lifetime. The solution is to use a temporary variable like this:

for (int i = 0; i < _threadCount; i++)
{
      var i1 = i;
      Thread thread = new Thread(() => WorkerThread(i1));
      thread.Start();
      _threads.Add(thread);
}

在此处阅读有关闭包的更多信息:闭包之美来自(Jon Skeet) 和 Lambda 表达式和从 (约瑟夫·阿尔巴哈里).

Read more about Closures here : The Beauty of Closures from (Jon Skeet) and Lambda expressions and captured variables from (Joseph Albahari).

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