File Save / Open Conflict

Question

I am trying to download a file to local storage then open that file.  The file saves okay and if I close/open the app the file works as expected.  However, if I try to open the file without closing the app first I get E_ACCESSDENIED.  It seems as though the file save is keeping a handle on the file but as far as I can tell I'm closing/disposing of everything I should be.  What am I missing?

thanks.

HttpClient httpClient = new HttpClient();
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, uri);
HttpResponseMessage response = await httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead);

// create a local file to save to
string filename = uri.Substring(uri.LastIndexOf("/") + 1, uri.Length - uri.LastIndexOf("/") - 1);
StorageFile imageFile = await folder.CreateFileAsync(filename, CreationCollisionOption.ReplaceExisting);
var ras = await imageFile.OpenAsync(FileAccessMode.ReadWrite);

// write the data to the file
DataWriter writer = new DataWriter(ras.GetOutputStreamAt(0));
writer.WriteBytes(await response.Content.ReadAsByteArrayAsync());

// close 
await writer.StoreAsync();
await writer.FlushAsync();
writer.DetachStream();

// cleanup
response.Dispose();
await ras.FlushAsync();
writer.Dispose();
ras.Dispose();

Answer 1

how are you opening the file? i tried with the launcher, which worked great. do you have a demo case we can play with so we can help?

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Microsoft Certified Solutions Developer - Windows Store Apps Using C#

Answer 2

This is how I open the file. The call my GetFile function works find, it is the OpenAsync to get the stream that returns the E_ACCESSDENIED.  

StorageFile audioFile = await App.GetFile(uri);

if(audioFile != null)

{

   var stream = await audioFile.OpenAsync(Windows.Storage.FileAccessMode.Read);

    // kablooey!

}

public async static Task<StorageFile> GetFile(string uri)
{
       string filename = uri.Substring(uri.LastIndexOf("/") + 1, uri.Length - uri.LastIndexOf("/") - 1);

       StorageFolder folder = await Windows.Storage.ApplicationData.Current.LocalFolder.CreateFolderAsync("fileCache", CreationCollisionOption.OpenIfExists);

       try
       {
             StorageFile file = await StorageFile.GetFileFromPathAsync(folder.Path + "\\" + filename);
             return file;
       }
       catch (Exception exc)
      {
           return null;
       }
}

Answer 3

can you post a sample so can see the entire flow?

---

Microsoft Certified Solutions Developer - Windows Store Apps Using C#

Answer 4

I finally figured it out.  The difference seems to be that I was creating the output stream inline and so didn't have a name to dispose of it with.  This code works great to write a file and tidy everything up properly.

public async Task DownloadFile(string uri, StorageFolder folder)
{
    try
    {
        // make the web call to get the file
        HttpClient httpClient = new HttpClient();
        HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, uri);
        HttpResponseMessage response = await httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead);

        // create a local file to save to
        string filename = uri.Substring(uri.LastIndexOf("/") + 1, uri.Length - uri.LastIndexOf("/") - 1);
        StorageFile file = await folder.CreateFileAsync(filename, CreationCollisionOption.ReplaceExisting);

        using (var ras = await file.OpenAsync(FileAccessMode.ReadWrite))
        {
            using (var outStream = ras.GetOutputStreamAt(0))
            {
                using (DataWriter writer = new DataWriter(outStream))
                {
                    writer.WriteBytes(await response.Content.ReadAsByteArrayAsync());

                    // close 
                    await writer.StoreAsync();
                    await writer.FlushAsync();
                    writer.DetachStream();

                    await ras.FlushAsync();

                    // cleanup
                    response.Dispose();
                    writer.Dispose();
                    ras.Dispose();
                }
           }
        }
    }
    catch (Exception exc)
    {
        string x = "y";
    }
}