任务吞噬抛出的异常 [英] Task swallows the exception thrown

问题描述

在下面的方法中，当TRY块中抛出异常时，它被吞噬。如何使它抛出异常，以便它被写入登录catch块？日志记录器工作正常。谢谢！

  public static bool MonitorQueueEmptyTask（string queueName，CancellationTokenSource tokenSource）
 {
 try 
 {
任务< bool> task = Task.Factory.StartNew< bool>（（）=> 
 {
 while（！QueueManager.IsQueueEmpty（queueName））
 {
 if（tokenSource.IsCancellationRequested） 
 {
 break; 
} 
 
 Thread.Sleep（5000）; 
抛出新的异常（抛出一个错误！）; //这个OW ED ED  - ;;;;; 
}; 
 
 return true; 
 
}，tokenSource.Token）; 
} 
 catch（Exception ex）
 {
 WriteExceptionToLog（ex.Stack）; //这不是这个方法不起作用。它工作正常
 
返回false; 
} 
 
返回true; 
} 
  

解决方案

忘了，你可以使用 ContinueWith 附加一个延续。目前的 try-catch 根本不会帮助您，因为例外是封装在任务之内。如果这是fire and forget，你可以记录例外：

  public static Task MonitorQueueEmptyTask（
 string queueName，CancellationTokenSource tokenSource）
 {
 return Task.Factory.StartNew< bool>（（）=> 
 {
 while（！QueueManager.IsQueueEmpty（queueName））
 {
 if（tokenSource.IsCancellationRequested）
 {
 break; 
} 
 
 Thread.Sleep（5000）; 
 throw new异常（抛出错误！）; 
}; 
}，tokenSource.Token，TaskCreationOptions.LongRunning）.ContinueWith（faultedTask => 
 {
 WriteExceptionToLog（faultedTask。异常）; 
}，TaskContinuationOptions.OnlyOnFaulted）; 
} 
  

反过来，在抛出异常之后不会传播异常，提供一种记录错误的机制。如果您希望由于某种原因重新抛出，可以注册到 TaskScheduler.UnobservedTaskException 并设置 ThrowUnobservedTaskExceptions enabled =true code>在您的配置。注意这个 ContinueWith ，因为一旦你看到 task.Exception 属性，它会考虑异常处理。 / p>


In the method below, when an exception is thrown in the TRY block, it is being swallowed. How can I make it throw the exception so that it gets written to log in the catch block? The log writer works fine. Thanks!

public static bool MonitorQueueEmptyTask(string queueName, CancellationTokenSource tokenSource)
{
    try
    {
        Task<bool> task = Task.Factory.StartNew<bool>(() =>
        {
            while (!QueueManager.IsQueueEmpty(queueName))
            {
                if (tokenSource.IsCancellationRequested)
                {                            
                    break;
                }

                Thread.Sleep(5000);
                throw new Exception("Throwing an error!"); //THIS THROW IS SWALLOWED -- NO LOG WRITTEN ON CATCH
            };

            return true;

        }, tokenSource.Token);
    }
    catch (Exception ex)
    {   
        WriteExceptionToLog(ex.Stack); //it's not that this method doesn't work. it works fine.

        return false;
    }

    return true;
}

解决方案

If you want to fire and forget, you can attach a continuation using ContinueWith. The current try-catch will not help you at all, as the exception is encapsulated inside the Task. If this is "fire and forget", than you can log the exception:

public static Task MonitorQueueEmptyTask(
                         string queueName, CancellationTokenSource tokenSource)
{
    return Task.Factory.StartNew<bool>(() =>
    {
        while (!QueueManager.IsQueueEmpty(queueName))
        {
            if (tokenSource.IsCancellationRequested)
            {                            
                break;
            }

            Thread.Sleep(5000);
            throw new Exception("Throwing an error!");
        };
    }, tokenSource.Token, TaskCreationOptions.LongRunning).ContinueWith(faultedTask =>
    {
        WriteExceptionToLog(faultedTask.Exception); 
    }, TaskContinuationOptions.OnlyOnFaulted); 
}

This, in turn, will not propagate the exception after it's thrown, but will provide a mechanism to log the error. If you want this to be re-thrown for some reason, you can register to TaskScheduler.UnobservedTaskException and set ThrowUnobservedTaskExceptions enabled="true" in your configuration. Note this ContinueWith, since it will consider the exception "handled" once you look at the task.Exception property.

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