在OnSuspending方法的过程中保存数据 [英] Saving data during the OnSuspending method

问题描述

对于C / XAML在Windows 8应用我有一些数据存储到LocalState文件夹。我在使用异步一些麻烦/等待操作者，我认为。

For a Windows 8 Application in C/XAML I have to store some data to the LocalState folder. I have some trouble using async/await operator I think.

在应用程序运行时，当我保存DATAS，一切工作正常，但是当我尝试OnSuspending方法中保存数据，似乎我的应用程序不会等待我的节能方法，完成暂停应用程序。

When I am saving datas while the application is running, everything works fine, but when I try to save the data during the OnSuspending method, it seems that my application doesn't wait for my saving method to be finished to suspend the application.

这个陌生人的事情是，当我调试，一步完成所有操作一步慢慢一切工作正常，但是当我不把任何断点，保存数据之前应用程序被关闭。

The stranger thing is that when I'm debugging and doing all the operation step by step slowly everything works fine, but when I don't put any breakpoints, the application is closed before the data are saved.

下面是我的code：

    private async void OnSuspending(object sender, SuspendingEventArgs e)
    {
        var deferral = e.SuspendingOperation.GetDeferral();
        await  api.BeforeClosing(true);
        deferral.Complete();
    }

    public async Task BeforeClosing(Boolean toTombstoning)
    {
            SaveItem<LoadingProgress>(fileNameLoadingProgress, InitLoading);
    }


    public static async void SaveItem<T>(String fileName, T data, Boolean crossThreadSecure = false) where T : IBinarySerializable
    {

            await CreateNewStorageFile(fileName);

            StorageFolder localFolder = Windows.Storage.ApplicationData.Current.LocalFolder;
            StorageFolder dataFolder = await localFolder.GetFolderAsync("Data");

            StorageFile file = await dataFolder.GetFileAsync(fileName);

            using (var stream = await file.OpenStreamForWriteAsync())
            {
                using (var writer = new BinaryWriter(stream))
                {
                    writer.Write<T>(data);
                }
            }
    }

    public async static Task CreateNewStorageFile(string filename)
    {
        StorageFolder localFolder = Windows.Storage.ApplicationData.Current.LocalFolder;
        StorageFolder dataFolder = await localFolder.CreateFolderAsync("Data", CreationCollisionOption.OpenIfExists);
        storage = await dataFolder.CreateFileAsync(filename, CreationCollisionOption.OpenIfExists);
    }

我做得不对的运营商的await？或者是那里，当我们可以暂停应用程序之前做一些操作的最大时间量？

Am I doing something wrong with the await operator? Or is there a maximum amount of time when we can do some operations before suspending the application?

感谢您

编辑：我做了一些新的考验：如果我删除deferral.Complete（）;从OnSuspending方法，这样可以节省数据很好（但从未显然关闭应用程序...）。我真的觉得问题是，我跑出来的时候，应用程序挂起。这真的看起来像在此线程的问题：<一href=\"http://stackoverflow.com/questions/11996288/storagefolder-createfileasync-crashes-when-called-from-app-onsuspending\">StorageFolder.CreateFileAsync从App.OnSuspending 调用时崩溃。但我已经试过了这个问题的全部解决方案，我仍然有问题...

EDIT : I made some new tests : If I remove deferral.Complete(); from the OnSuspending method, it saves the data well (but never close the app obviously...). I really think the problem is that I run out of time when the application is suspending. It really looks like the problem on this thread : StorageFolder.CreateFileAsync crashes when called from App.OnSuspending. But I have tried all the solutions of this question and I still have the problem...

推荐答案

您的问题是，你打电话完成之前的所有异步操作完成。

Your problem is that you're calling Complete before all your async operations have completed.

最简单的办法是让 SaveItem 的异步任务方法，而不是异步无效，然后等待它 BeforeClosing 。

The simplest solution is to make SaveItem an async Task method instead of async void, and then await it in BeforeClosing.

作为一般规则，异步方法应该总是返回工作 / 任务＆LT; T＆GT ; 除非有无的返回无效（例如，事件处理程序）

As a general rule, async methods should always return Task/Task<T> unless they have to return void (e.g., event handlers).

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