集合对象中线程安全_什么是线程安全的集合_线程安全的集合类

using System;
using System.Collections.Generic;
using System.Threading;
 
namespace CollSecExp
{
    class Program
    {        
        static void Main(string[] args)
        {
            List<int> list = new List<int>();
            for (int i = 0; i < 10; i)
            {
                list.Add(i);
            }

            Thread t1 = new Thread(() =>
            {
                 foreach (var item in list)
                 {
                     Console.WriteLine("t1.item:{0}", item);
                     Thread.Sleep(1000);
                 }
            });
            t1.Start();

            Thread t2 = new Thread(() =>
            {
                Thread.Sleep(1000);
                list.RemoveAt(1);
                list.RemoveAt(3);
                foreach (var item in list)
                {
                     Console.WriteLine("t2.item:{0}", item);
                 }
            });
            t2.Start();
        }
    }
}

运行示例代码1，会抛出InvalidOperationException异常，提示“集合已修改；可能无法执行枚举操作。”

这是因为，线程2移除index=1，3的元素导致集合被修改，很显然，此时线程1遍历集合肯定会出错，因为它这时遍历得到的结果与实际情况已经不符，就算取出也没有了价。

针对这种情况，我们可以对集合加锁来保证线程对集合操作的同步。

using System;
using System.Collections.Generic;
using System.Threading;
 
namespace CollSecExp
{
    class Program
    {        
        static void Main(string[] args)
        {
            object sycObj = new object();
            List<int> list = new List<int>();
            for (int i = 0; i < 10; i)
            {
                list.Add(i);
            }
 
            Thread t1 = new Thread(() =>
            {
                lock (sycObj)
                {
                    foreach (var item in list)
                    {
                        Console.WriteLine("t1.item:{0}", item);
                        Thread.Sleep(1000);
                    }
                }
            });
            t1.Start();

            Thread t2 = new Thread(() =>
            {
                Thread.Sleep(1000);
                lock (sycObj)
                {
                    list.RemoveAt(1);
                    list.RemoveAt(3);
                    foreach (var item in list)
                    {
                        Console.WriteLine("t2.item:{0}", item);
                    }
               }
            });
            t2.Start();
        }
    }
}

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