无需等待就调用异步方法 [英] Call async method without await

问题描述

我致力于Windows Phone 8+应用程序的图像加载器库，当然它支持磁盘上的缓存.

I working on image loader library for Windows Phone 8+ applications, and of course it supports caching on disk.

因此，我需要异步将图像保存在磁盘上，而无需等待结果:

So, I need to save image on disk asynchronously without awaiting result:

// Async saving to the storage cache without await
// ReSharper disable once CSharpWarnings::CS4014
Config.StorageCacheImpl.SaveAsync(imageUrl, downloadResult.ResultStream)
    .ContinueWith(
        task => 
        {
            if (task.IsFaulted || !task.Result)
            {
                Log("[error] failed to save in storage: " + imageUri);
            }
        }
);

如您所见，SaveAsync()是异步方法，它返回Task<bool>，如果保存图像，则bool结果为true.

As you can see, SaveAsync() is async method and it returns Task<bool>, where bool result is true if image was saved.

问题是编译器显示警告，因为我没有在等待异步方法的结果，但是，我不需要等待，我需要返回调用SaveAsync()后，将下载的图像尽快地下载到用户代码中.

The problem is that compiler shows warning because I am not awaiting the result of the async method, but, I do not need to await it, i need to return downloaded image to the user code as fast as it possible, after invoke of SaveAsync() I return downloaded image.

所以我正在异步将图像缓存到IsolatedStorageFile ，而且-没关系，是否缓存，因为如果没有，JetImageLoader会再次加载它.

So I am caching image to the IsolatedStorageFile asynchronously and moreover — it does not matter, will it be cached or not, because if not — JetImageLoader will load it again.

是否可以禁用此警告?

P.S.如果您想查看JetImageLoader的资源，我可以给您一个指向GitHub的链接.

P.S. if you want to see JetImageLoader sources, I can give you a link to GitHub.

推荐答案

出现编译器警告是因为这样做几乎总是一个错误.一方面，您不会收到有关任务已完成的任何通知，也不会收到有关错误的通知.

The compiler warning is there because it's almost always a mistake to do this. For one thing, you don't get any kind of notification that the task completed, and you also don't get notified of errors.

为避免编译器警告，您可以将其分配给未使用的局部变量，如下所示:

To avoid the compiler warning, you can just assign it to an unused local variable, like this:

var _ = Config.StorageCacheImpl.SaveAsync...

对于您而言，我还建议您使用辅助方法而不是ContinueWith来使代码更简洁:

In your case, I'd also recommend using a helper method instead of ContinueWith to make the code a little cleaner:

private static async Task SaveAsync(string imageUrl, Stream resultStream)
{
  bool success = false;
  try
  {
    success = await Config.StorageCacheImpl.SaveAsync(imageUrl, downloadResult.ResultStream);
  }
  finally
  {
    if (!success)
      Log("[error] failed to save in storage: " + imageUri);
  }
}

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