螺纹参数被修改 [英] Thread parameters being changed

问题描述

在启动多个线程，我解析 ID 参数有时是错误的。这里是我的启动：

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);
}

和我的线程函数：

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

这段代码的输出是：

The output of this code is:

[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

凡在我的脑海里，此代码应创建的每个线程有独特 ID ，而不是如上面看到重复的。

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：

目标平台：64

目标框架：.NET框架4.5

Target Framework: .NET Framework 4.5

推荐答案

您应该小心意外修改捕获的变量，如 I 启动线程，因为 I 为后的共享即可。在 I 变量是指在相同的内存位置在整个循环的寿命。在解决方案是使用的临时变量的是这样的：

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);
}

了解更多的瓶盖的位置：瓶盖从美（乔恩斯基特的）和的 Lambda表达式并抓获从（约瑟夫阿尔巴哈利的）。

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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