Building a corrupted zip file using ASP.Net core and Angular 6

Question

I'm using Angular 6 and ASP.Net core, i have a web api where i build an archive (zip) file that i return to angular, and start a download operation.

I'm facing two problems:

The first is that the archive can only be extracted using a compression software (7zip for example) but cannot be accessed through windows 10 functionality:

Error message: "windows cannot open the folder. The compressed (zipped) folder 'xx' is invalid"

The other zip files on my machine work just fine.

The second problem is that my code works if i return a byte array, but doesn't work when i return a memoryStream (i get some CORS error in the second case)

Here is some parts of the code i use (i will only post some relevant parts of the code) :

in Angular (6) i post like this:

this.post<T>(url, content,
   {
       headers: new HttpHeaders({ 'Accept': 'application/x-zip-compressed', 
                'Content-Type': 'application/json' }),
       observe: 'body',
       responseType: 'blob'
   }
)

in the ASP.NET core api:

// In the Controller
// init some variables and stuff..
var fileName...
var paths..  // a list of paths to my files

new FileExtensionContentTypeProvider().TryGetContentType(fileName, out contentType);
return File(FileService.ZipFiles(paths).ToArray(), contentType, fileName);
// here, note that contentType would be 'application/x-zip-compressed'. also note the ToArray()

and in the file service, i do the following:

using (var zipMemoryStream = new MemoryStream())
{
    var zipArchive = new ZipArchive(zipMemoryStream, ZipArchiveMode.Create);
    foreach (var path in filePaths)
    {
        // some checks on file existance here..


        ZipArchiveEntry entry = zipArchive.CreateEntry(Path.GetFileName(path));
        using (var entryStream = entry.Open())
        using (var fileStream = File.Open(path, FileMode.Open, FileAccess.Read))
        {
            fileStream.CopyTo(entryStream);
        }
    }

    zipMemoryStream.Position = 0;

    // here i return the memory stream, but i have to convert it to a byte 
    // array in the return of the controller above for it to work
    return zipMemoryStream;
}

Edit:

When analysing the file using 7zip, it says as an error:

unexpected end of data

You very likely don’t want to dispose the memory stream (i.e. wrap it in a `using`) when you actually want to return it from your service. — poke, Aug 08 '18 at 07:41

score 2 · Answer 1 · answered Aug 08 '18 at 09:38

Solved using the answer provided in this SO question:

ZipArchive gives Unexpected end of data corrupted error

Basically, i had to change the portion of FileService code (that i provided in the question) to this:

using (var zipMemoryStream = new MemoryStream())
{
    //  --> put the zip archive in a using block
    using(var zipArchive = new ZipArchive(zipMemoryStream, ZipArchiveMode.Create))
    {
        foreach (var path in filePaths)
        {
            // some checks on file existance here..


            ZipArchiveEntry entry = zipArchive.CreateEntry(Path.GetFileName(path));
            using (var entryStream = entry.Open())
            using (var fileStream = File.Open(path, FileMode.Open, FileAccess.Read))
            {
                fileStream.CopyTo(entryStream);
            }
        }
    }

    // --> return a byte array AFTER the using block of the zipArchive
    return zipMemoryStream.ToArray();
}

(i used the // --> to show the edited parts of the code)

You saved the day I also needed `leaveOpen: true` to keep `MemoryStream` open after disposing the `ZipArchive` — Fabio, Jan 27 '21 at 12:18

Building a corrupted zip file using ASP.Net core and Angular 6

1 Answers1

Linked