c# - 多线程行为奇怪的 C#!

Question

这是我的应用程序，用于执行线程示例，但输出与预期不符，请有人对此有任何线索

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
namespace OTS_Performence_Test_tool
{
    class Program
    {

        static void testThread(string    xx)
        {

            int count = 0;
            while (count < 5)
            {
                Console.WriteLine(xx );
                count++;

            }
        }

        static void Main(string[] args)
        {
            Console.WriteLine("Hello to the this test app ---");

            for (int i = 1; i<=3; i++)
            {

                    Thread thread = new Thread(() => testThread("" + i + "__"));

                thread.Start();

            }


            Console.ReadKey();
        }
    }
}

但出来却是

3__

3__

3__

3__

3__

3__

3__

3__

3__

3__

4__

4__

4__

4__

4__

到底发生了什么任何人都可以解释 谢谢

Answer 1

See Eric Lippert's excellent blog post on this issue.

这是由访问 "modified closure" 引起的.

将循环的主体更改为:

for (int i = 1; i<=3; i++)
{
    int j = i;  // Prevent use of modified closure.
    Thread thread = new Thread(() => testThread("" + j + "__"));

    thread.Start();
}

(请注意，对于 foreach 循环，这已在 .Net 4.5 中得到修复，但对于 for 循环则未修复。)