Save to isolated storage directly in WP8

Question

I want to save a zip file directly to isolated storage from server , But the problem i am facing was when i try to save using the below code , i get out of memory exception since my file size is > 150 MB some times. So i posted a question here and the suggestion was

you can download such a file directly to IsolatedStorage, but if you want to put that into Memory - there can be a problem.

So how can i save a file from server directly to isolated storage without saving to memory . The code i used is posted here

client = new WebClient();
    client.OpenReadCompleted += new OpenReadCompletedEventHandler(client_OpenReadCompleted);
    client.OpenReadAsync(new Uri(fileurl), objRef);

    private async void client_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)
    {

            var file = IsolatedStorageFile.GetUserStoreForApplication();
            if (!file.DirectoryExists("Folderpath/Files"))
            {
                file.CreateDirectory("Folderpath/Files");
            }
            string hpubFile = "/Folderpath/Files/fileName" ;
            using (IsolatedStorageFileStream stream = new IsolatedStorageFileStream(hpubFile, System.IO.FileMode.OpenOrCreate, FileAccess.ReadWrite, file))
            {
                byte[] buffer = new byte[1024];
                while (e.Result.Read(buffer, 0, buffer.Length) > 0)
                {
                    stream.Write(buffer, 0, buffer.Length);
                }
            }
        }
    }

You are getting the data from your server and you want to save in your App and that is of big size — Dragon
Try setting the AllowReadStreamBuffering property of the WebClient to false, otherwise it will download the whole file before raising the OpenReadCompleted event — Kevin Gosse
@Dragon Yes exactly ,i want to save the zip from a remote url to isolated storage and size of zip file is not a fixes one . it may vary from 10 Mb to 500 MB — Sebastian
@JMat @KooKiz is right, first try to use code you already have: stackoverflow.com/questions/21572276/… , just add in your DownloadFIle, before OpenReadComleted wc.AllowReadStreamBuffering = false; In the answer I've posted stream is read async, then only buffer amount should be in memory, — Romasz
@Romasz i am getting this exception Read is not supported on the main thread when buffering is disabled.If you want i can share full code — Sebastian

Romasz Romasz · Accepted Answer · 2014-02-10T10:02:33

Then maybe try such an approach - do it with HttpWebRequest:

1. First extend your HttpWebRequest with awaitable GetResponseAsync - WP lacks this method, but with TaskCompletitionSource you can write your own implementation. Somwhere in your Namespace, make a static class:

public static class Extensions
{
    public static Task<HttpWebResponse> GetResponseAsync(this HttpWebRequest webRequest)
    {
        TaskCompletionSource<HttpWebResponse> taskComplete = new TaskCompletionSource<HttpWebResponse>();
        webRequest.BeginGetResponse(
            asyncResponse =>
            {
                try
                {
                    HttpWebRequest responseRequest = (HttpWebRequest)asyncResponse.AsyncState;
                    HttpWebResponse someResponse = (HttpWebResponse)responseRequest.EndGetResponse(asyncResponse);
                    taskComplete.TrySetResult(someResponse);
                }
                catch (WebException webExc)
                {
                    HttpWebResponse failedResponse = (HttpWebResponse)webExc.Response;
                    taskComplete.TrySetResult(failedResponse);
                }
                catch (Exception exc) { taskComplete.SetException(exc); }
            }, webRequest);
        return taskComplete.Task;
    }
}

2. Then modify your code to use it:

CancellationTokenSource cts = new CancellationTokenSource();
enum Problem { Ok, Cancelled, Other };

public async Task<Problem> DownloadFileFromWeb(Uri uriToDownload, string fileName, CancellationToken cToken)
{
    try
    {
        HttpWebRequest wbr = WebRequest.CreateHttp(uriToDownload);
        wbr.Method = "GET";
        wbr.AllowReadStreamBuffering = false;
        WebClient wbc = new WebClient();

        using (HttpWebResponse response = await wbr.GetResponseAsync())
        {
            using (Stream mystr = response.GetResponseStream())
            {
                using (IsolatedStorageFile ISF = IsolatedStorageFile.GetUserStoreForApplication())
                  {
                      if (ISF.FileExists(fileName)) return Problem.Other;
                      using (IsolatedStorageFileStream file = ISF.CreateFile(fileName))
                      {
                          const int BUFFER_SIZE = 100 * 1024;
                          byte[] buf = new byte[BUFFER_SIZE];

                          int bytesread = 0;
                          while ((bytesread = await mystr.ReadAsync(buf, 0, BUFFER_SIZE)) > 0)
                          {
                              cToken.ThrowIfCancellationRequested();
                              file.Write(buf, 0, bytesread);
                          }
                      }
                  }
                  return Problem.Ok;
              }
          }
      }
      catch (Exception exc)
      {
          if (exc is OperationCanceledException)
              return Problem.Cancelled;
          else return Problem.Other; 
      }
  }

3. And download:

  private async void Downlaod_Click(object sender, RoutedEventArgs e)
  {
      cts = new CancellationTokenSource();
      Problem fileDownloaded = await DownloadFileFromWeb(new Uri(@"http://filedress/myfile.txt", UriKind.Absolute), "myfile.txt", cts.Token);
      switch(fileDownloaded)
      {
          case Problem.Ok:
              MessageBox.Show("Problem with download");
              break;
          case Problem.Cancelled:
              MessageBox.Show("Download cancelled");
              break;
          case Problem.Other:
          default:
              MessageBox.Show("Other problem with download");
              break;
      }
  }

As I've my WebResponse, I get a stream from it and then read it async.
Please be aware that I've not tested the code above, but hopefuly it may give you some ideas how this can work.

Save to isolated storage directly in WP8

2 Answers