How do I ZIP a file in C#, using no 3rd-party APIs?

Question

I'm pretty sure this is not a duplicate so bear with me for just a minute.

How can I programatically (C#) ZIP a file (in Windows) without using any third party libraries? I need a native windows call or something like that; I really dislike the idea of starting a process, but I will if I absolutely have to. A PInovke call would be much better.

Failing that, let me tell you what I'm really trying to accomplish: I need the ability to let a user download a collection of documents in a single request. Any ideas on how to accomplish this?

Answer 1

How can I programatically (C#) ZIP a file (in Windows) without using any third party libraries?

If using the 4.5+ Framework, there is now the ZipArchive and ZipFile classes.

using (ZipArchive zip = ZipFile.Open("test.zip", ZipArchiveMode.Create))
{
    zip.CreateEntryFromFile(@"c:\something.txt", "data/path/something.txt");
}

You need to add references to:

• System.IO.Compression
• System.IO.Compression.FileSystem

For .NET Core targeting net46, you need to add dependencies for

• System.IO.Compression
• System.IO.Compression.ZipFile

Example project.json:

"dependencies": {
  "System.IO.Compression": "4.1.0",
  "System.IO.Compression.ZipFile": "4.0.1"
},

"frameworks": {
  "net46": {}
}

For .NET Core 2.0, just adding a simple using statement is all that is needed:

• using System.IO.Compression;

Answer 2

Are you using .NET 3.5? You could use the ZipPackage class and related classes. Its more than just zipping up a file list because it wants a MIME type for each file you add. It might do what you want.

I'm currently using these classes for a similar problem to archive several related files into a single file for download. We use a file extension to associate the download file with our desktop app. One small problem we ran into was that its not possible to just use a third-party tool like 7-zip to create the zip files because the client side code can't open it -- ZipPackage adds a hidden file describing the content type of each component file and cannot open a zip file if that content type file is missing.

Answer 3

    private static string CompressFile(string sourceFileName)
    {
        using (ZipArchive archive = ZipFile.Open(Path.ChangeExtension(sourceFileName, ".zip"), ZipArchiveMode.Create))
        {
            archive.CreateEntryFromFile(sourceFileName, Path.GetFileName(sourceFileName));
        }
        return Path.ChangeExtension(sourceFileName, ".zip");
    }

Answer 4

I was in the same situation, wanting to .NET instead of a third party library. As another poster mentioned above, simply using the ZipPackage class (introduced in .NET 3.5) is not quite enough. There is an additional file that MUST be included in the archive in order for the ZipPackage to work. If this file is added, then the resulting ZIP package can be opened directly from Windows Explorer - no problem.

All you have to do is add the [Content_Types].xml file to the root of the archive with a "Default" node for every file extension you wish to include. Once added, I could browse the package from Windows Explorer or programmatically decompress and read its contents.

More information on the [Content_Types].xml file can be found here: http://msdn.microsoft.com/en-us/magazine/cc163372.aspx

Here is a sample of the [Content_Types].xml (must be named exactly) file:

<?xml version="1.0" encoding="utf-8" ?>
<Types xmlns=
    "http://schemas.openxmlformats.org/package/2006/content-types">
  <Default Extension="xml" ContentType="text/xml" /> 
  <Default Extension="htm" ContentType="text/html" /> 
  <Default Extension="html" ContentType="text/html" /> 
  <Default Extension="rels" ContentType=
    "application/vnd.openxmlformats-package.relationships+xml" /> 
  <Default Extension="jpg" ContentType="image/jpeg" /> 
  <Default Extension="png" ContentType="image/png" /> 
  <Default Extension="css" ContentType="text/css" /> 
</Types>

And the C# for creating a ZIP file:

var zipFilePath = "c:\\myfile.zip"; 
var tempFolderPath = "c:\\unzipped"; 

    using (Package package = ZipPackage.Open(zipFilePath, FileMode.Open, FileAccess.Read)) 
    { 
        foreach (PackagePart part in package.GetParts()) 
        { 
            var target = Path.GetFullPath(Path.Combine(tempFolderPath, part.Uri.OriginalString.TrimStart('/'))); 
            var targetDir = target.Remove(target.LastIndexOf('\\')); 

            if (!Directory.Exists(targetDir)) 
                Directory.CreateDirectory(targetDir); 

            using (Stream source = part.GetStream(FileMode.Open, FileAccess.Read)) 
            { 
                source.CopyTo(File.OpenWrite(target)); 
            } 
        } 
    } 

Note:

• This code uses the Stream.CopyTo method in .NET 4.0
• This will become much simpler with the introduction of the ZipArchive class in .NET 4.5: http://msdn.microsoft.com/en-us/library/system.io.compression.ziparchive(v=vs.110).aspx

Answer 5

Based off Simon McKenzie's answer to this question, I'd suggest using a pair of methods like this:

    public static void ZipFolder(string sourceFolder, string zipFile)
    {
        if (!System.IO.Directory.Exists(sourceFolder))
            throw new ArgumentException("sourceDirectory");

        byte[] zipHeader = new byte[] { 80, 75, 5, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

        using (System.IO.FileStream fs = System.IO.File.Create(zipFile))
        {
            fs.Write(zipHeader, 0, zipHeader.Length);
        }

        dynamic shellApplication = Activator.CreateInstance(Type.GetTypeFromProgID("Shell.Application"));
        dynamic source = shellApplication.NameSpace(sourceFolder);
        dynamic destination = shellApplication.NameSpace(zipFile);

        destination.CopyHere(source.Items(), 20);
    }

    public static void UnzipFile(string zipFile, string targetFolder)
    {
        if (!System.IO.Directory.Exists(targetFolder))
            System.IO.Directory.CreateDirectory(targetFolder);

        dynamic shellApplication = Activator.CreateInstance(Type.GetTypeFromProgID("Shell.Application"));
        dynamic compressedFolderContents = shellApplication.NameSpace(zipFile).Items;
        dynamic destinationFolder = shellApplication.NameSpace(targetFolder);

        destinationFolder.CopyHere(compressedFolderContents);
    }
}