CreateFileAsync UnauthorizedAccessException

本文关键字：UnauthorizedAccessException CreateFileAsync | 更新日期: 2023-09-27 18:11:41

我有以下代码，从我的Windows 8应用程序的web服务器获取动态图像。

        private async Task httpFetcher()
    {
        HttpClient httpClient = new HttpClient();
        HttpRequestMessage request = new HttpRequestMessage(
HttpMethod.Get, "http://www.reignofcomputer.com/imgdump/sample.png");
        HttpResponseMessage response = await httpClient.SendAsync(request,
            HttpCompletionOption.ResponseHeadersRead);
        Uri imageUri;
        BitmapImage image = null;
            var imageFile = await ApplicationData.Current.LocalFolder.CreateFileAsync(
         "sample.png", CreationCollisionOption.ReplaceExisting);
            var fs = await imageFile.OpenAsync(FileAccessMode.ReadWrite);
            DataWriter writer = new DataWriter(fs.GetOutputStreamAt(0));
            writer.WriteBytes(await response.Content.ReadAsByteArrayAsync());
            await writer.StoreAsync();
            writer.DetachStream();
            await fs.FlushAsync();
            writer.Dispose();
            if (Uri.TryCreate(imageFile.Path, UriKind.RelativeOrAbsolute, out imageUri))
            {
                image = new BitmapImage(imageUri);
            }
        image1.Source = image;
    }

这在大多数情况下都有效，但由于某些原因，有时我得到

UnauthorizedAccessException (0x80070005, E_ACCESSDENIED)， HResult .日志含义-2147024891 .

因为错误是随机的，它通常工作，我不确定问题出在哪里。

CreateFileAsync UnauthorizedAccessException

我最近有同样的问题，经过一些测试，我发现这是因为一些程序可能会删除文件，而你试图访问它。下面是我做测试的方法。

  static void Main(string[] args)
    {
        Thread t1 = new Thread(Create);
        Thread t2 = new Thread(Delete);
        t1.Start();
        t2.Start();
    }

    private static void Create()
    {
        int i = 0;
        try
        {
            while (true)
            {
                System.IO.TextWriter writer = new System.IO.StreamWriter("file.txt");
                i++;
                System.Console.Out.WriteLine(i);
                writer.Write(i);
                writer.Close();
            }
        }
        catch (System.UnauthorizedAccessException ex)
        {
            System.Console.Out.WriteLine("Boom at: " + i.ToString());
        }

    }
    private static void Delete()
    {
        while (true)
        {
            try
            {
                System.IO.File.Delete("file.txt");
            }
            catch (UnauthorizedAccessException ex)
            {
            }
            catch (Exception e)
            { }
        }
    }