c# - 运行多个任务重用同一个对象实例

Question

这是一个有趣的。我有一个创建一堆Tasks 的服务。目前，列表中只配置了两个任务。但是，如果我在操作中放置一个断点Task并检查 的值schedule.Name，它会以相同的计划名称被命中两次。但是，配置了两个单独的计划并在计划列表中。谁能解释为什么任务重用循环中的最后一个时间表？这是范围问题吗？

// make sure that we can log any exceptions thrown by the tasks
TaskScheduler.UnobservedTaskException += new EventHandler<UnobservedTaskExceptionEventArgs>(TaskScheduler_UnobservedTaskException);

// kick off all enabled tasks
foreach (IJobSchedule schedule in _schedules)
{
    if (schedule.Enabled)
    {
        Task.Factory.StartNew(() =>
                                {
                                    // breakpoint at line below. Inspecting "schedule.Name" always returns the name 
                                    // of the last schedule in the list. List contains 2 separate schedule items.
                                    IJob job = _kernel.Get<JobFactory>().CreateJob(schedule.Name);
                                    JobRunner jobRunner = new JobRunner(job, schedule);
                                    jobRunner.Run();
                                },
                                CancellationToken.None, 
                                TaskCreationOptions.LongRunning, 
                                TaskScheduler.Default
                                );
    }
} // next schedule

Answer 1

如果您在 foreach 循环中使用临时变量，它应该可以解决您的问题。

foreach (IJobSchedule schedule in _schedules)
{
    var tmpSchedule = schedule;
    if (tmpSchedule.Enabled)
    {
        Task.Factory.StartNew(() =>
                                {
                                    // breakpoint at line below. Inspecting "schedule.Name" always returns the name 
                                    // of the last schedule in the list. List contains 2 separate schedule items.
                                    IJob job = _kernel.Get<JobFactory>().CreateJob(tmpSchedule.Name);
                                    JobRunner jobRunner = new JobRunner(job, tmpSchedule);
                                    jobRunner.Run();
                                },
                                CancellationToken.None, 
                                TaskCreationOptions.LongRunning, 
                                TaskScheduler.Default
                                );
    }


} //

有关闭包和循环变量的更多参考，请参阅 关闭被认为有害的循环变量