Question

I am working on a Windows Store app proof of concept that will open a .zip file and extract the contents to an app-specific Roaming folder. I have looked into several popular libraries to extract the contents only to find that these libraries don’t support Windows Store apps (at least not yet). So, I have decided to go with ZipArchive. I have the following code in a button click handler:

private async void Button_Click_1(object sender, RoutedEventArgs e)
{
    var fileOpenPicker = new FileOpenPicker();
    fileOpenPicker.FileTypeFilter.Add(".zip");
    var openedFile = await fileOpenPicker.PickSingleFileAsync();

    var booksFolder = await Windows.Storage.ApplicationData.Current.RoamingFolder.CreateFolderAsync("Stuff", CreationCollisionOption.OpenIfExists);
    var folder = await booksFolder.CreateFolderAsync(openedFile.Name.Replace(".zip", string.Empty), CreationCollisionOption.ReplaceExisting);

    using (var stream = await openedFile.OpenStreamForReadAsync())
    {
        using (var zip = new ZipArchive(stream, ZipArchiveMode.Read))
        {
            foreach (var entry in zip.Entries)
            {
                using (var entryStream = entry.Open())
                {
                    var file = await folder.CreateFileAsync(entry.Name);
                    using (var decompressedStream = await file.OpenStreamForWriteAsync())
                    {
                        using (var deflateStream = new DeflateStream(entryStream, CompressionMode.Decompress))
                        {
                            await deflateStream.CopyToAsync(decompressedStream, (int)entry.Length);
                        }
                    }
                }
            }
        }
    }
}

However, I get an InvalidDataException on the line

await deflateStream.CopyToAsync(decompressedStream, (int)entry.Length);

Here’s the details of the exception:

System.IO.InvalidDataException was unhandled by user code
  HResult=-2146233087
  Message=Unknown block type. Stream might be corrupted.
  Source=System
  StackTrace:
       at System.IO.Compression.DeflateStream.EndRead(IAsyncResult asyncResult)
       at System.IO.Stream.<BeginEndReadAsync>b__e(Stream stream, IAsyncResult asyncResult)
       at System.Threading.Tasks.TaskFactory`1.FromAsyncTrimPromise`1.Complete(TInstance thisRef, Func`3 endMethod, IAsyncResult asyncResult, Boolean requiresSynchronization)
    --- End of stack trace from previous location where exception was thrown ---
       at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
       at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
       at System.IO.Stream.<CopyToAsyncInternal>d__2.MoveNext()
    --- End of stack trace from previous location where exception was thrown ---
       at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
       at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
       at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
       at POC.MoviePlayer.GroupedItemsPage.<Button_Click_1>d__4.MoveNext() in c:\Users\Brent\Documents\Visual Studio 2012\Projects\POC.MoviePlayer\POC.MoviePlayer\GroupedItemsPage.xaml.cs:line 108
  InnerException: 

The .zip file I am trying to import was created with Windows Explorer’s Send To Compressed (Zipped) Folder option. I have also tried to create a .zip file in code, using ZipArchive, but I get more exceptions with that code too. Since that isn’t my ideal use case anyway, I won’t include my code to create the .zip unless it turns out to be useful to somebody.

I am hoping somebody can either see the error of my ways in the code above or provide a link to a solid library to work with zip files that is preferably open source. This frustrated developer would be very grateful for any help.

Answer 1

You don’t have to decompress the result of entry.Open(). It is already decompressed.

You could also use ZipFileExtensions.ExtractToDirectory (http://msdn.microsoft.com/en-us/library/system.io.compression.zipfileextensions.extracttodirectory.aspx) to simplify your code.