StorageFile.OpenAsync中的UnauthorizedAccessException

问题描述

我使用下面的代码来下载/保存图像并稍后打开它，但是在以后的OpenAsync中，它会抛出UnauthorizedAccessException，似乎文件没有关闭，但实际上IRandomAccessStream / DataWriter已被处理掉了。

I used the following code to download/save an image and open it later, but in later OpenAsync, it throws the UnauthorizedAccessException, it seems that the file is not close, but actually the IRandomAccessStream/DataWriter has been disposed.

HttpClient httpClient = new HttpClient();
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, "http://www.silverlightshow.net/Storage/Users/nikolayraychev/Perspective_Transforms_4.gif");
HttpResponseMessage response = await httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead);

//Write Image File
StorageFile imageFile = await ApplicationData.Current.LocalFolder.CreateFileAsync("test.gif", CreationCollisionOption.ReplaceExisting);
using (IRandomAccessStream fs = await imageFile.OpenAsync(FileAccessMode.ReadWrite))
{
    using (DataWriter writer = new DataWriter(fs.GetOutputStreamAt(0)))
    {
        writer.WriteBytes(await response.Content.ReadAsByteArrayAsync());
        await writer.StoreAsync();
        writer.DetachStream();
        await fs.FlushAsync();
    }
 }

 StorageFile imageFile1 = await ApplicationData.Current.LocalFolder.GetFileAsync("test.gif");
 //Exception is throwed here
 using (IRandomAccessStream stream = await imageFile1.OpenAsync(FileAccessMode.Read))
 {
     BitmapImage img = new BitmapImage();
     img.SetSource(stream);
}

推荐答案

我遇到了同样的问题，必须在流完成之前明确地处理流和文件对象。

I had the same issue and had to explicitly dispose the stream and file objects before it would complete.

    var file = await ApplicationData.Current.LocalFolder.CreateFileAsync(filename, Windows.Storage.CreationCollisionOption.ReplaceExisting);
    using (var fs = await file.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite))
    {
        var outStream = fs.GetOutputStreamAt(0);
        var dataWriter = new Windows.Storage.Streams.DataWriter(outStream);
        dataWriter.WriteString("Hello from Test!");
        await dataWriter.StoreAsync();
        dataWriter.DetachStream();
        await outStream.FlushAsync();
        outStream.Dispose(); //
        fs.Dispose();
    }

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