Metro App FileIO.WriteTextAsync多线程 [英] Metro App FileIO.WriteTextAsync Multiple Threads

问题描述

我有一个经常从多个线程调用的方法.它涉及使用await FileIO.WriteTextAsync写入磁盘.从单个线程调用它时，它的工作效果很好，但是一旦我在多个线程中开始执行此操作，就会收到此错误:

I have a method which is called frequently from multiple threads. It involves writing to disk using await FileIO.WriteTextAsync. This works fine when it is called from a single thread, but once I start doing this in multiple threads, I get this error:

The process cannot access the file because it is being used by another process.

我知道错误的含义，但是我不确定如何解决.通常，我将创建一个lock(object)语句，以确保一次仅由一个线程访问该文件.但是，这是一个异步方法，因此我不能在lock(object)语句的主体中使用await运算符.

I know what the error means, but I'm not sure how to work around it. Normally, I would create a lock(object) statement, to ensure that the file is being accessed by only one thread at a time. However, this is an asynchronous method and as such I can't use the await operator in the body of the lock(object) statement.

请提供有关如何处理这种情况的建议.

Please advise on how to handle this scenario.

推荐答案

您可以使用SemaphoreSlim充当async兼容的锁:

You can use SemaphoreSlim to act as an async-compatible lock:

SemaphoreSlim _mutex = new SemaphoreSlim(1);

async Task MyMethodAsync()
{
  await _mutex.WaitAsync();
  try
  {
    ...
  }
  finally
  {
    _mutex.Release();
  }
}

我个人不喜欢finally，所以我通常编写自己的IDisposable以便在处置时释放互斥量，并且我的代码可以如下所示:

Personally, I don't like the finally, so I usually write my own IDisposable to release the mutex when disposed, and my code can look like this:

async Task MyMethodAsync()
{
  // LockAsync is an extension method returning my custom IDisposable
  using (await _mutex.LockAsync()) 
  {
    ...
  }
}

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