Zip folder in C#

Question

This answer changes with .NET 4.5. Creating a zip file becomes incredibly easy. No third-party libraries will be required.

string startPath = @"c:\example\start";
string zipPath = @"c:\example\result.zip";
string extractPath = @"c:\example\extract";

ZipFile.CreateFromDirectory(startPath, zipPath);
ZipFile.ExtractToDirectory(zipPath, extractPath);

From the DotNetZip help file, http://dotnetzip.codeplex.com/releases/

using (ZipFile zip = new ZipFile())
{
   zip.UseUnicodeAsNecessary= true;  // utf-8
   zip.AddDirectory(@"MyDocuments\ProjectX");
   zip.Comment = "This zip was created at " + System.DateTime.Now.ToString("G") ; 
   zip.Save(pathToSaveZipFile);
}

There's nothing in the BCL to do this for you, but there are two great libraries for .NET which do support the functionality.

• SharpZipLib
• DotNetZip

I've used both and can say that the two are very complete and have well-designed APIs, so it's mainly a matter of personal preference.

I'm not sure whether they explicitly support adding Folders rather than just individual files to zip files, but it should be quite easy to create something that recursively iterated over a directory and its sub-directories using the DirectoryInfo and FileInfo classes.

In .NET 4.5 the ZipFile.CreateFromDirectory(startPath, zipPath); method does not cover a scenario where you wish to zip a number of files and sub-folders without having to put them within a folder. This is valid when you wish the unzip to put the files directly within the current folder.

This code worked for me:

public static class FileExtensions
{
    public static IEnumerable<FileSystemInfo> AllFilesAndFolders(this DirectoryInfo dir)
    {
        foreach (var f in dir.GetFiles())
            yield return f;
        foreach (var d in dir.GetDirectories())
        {
            yield return d;
            foreach (var o in AllFilesAndFolders(d))
                yield return o;
        }
    }
}

void Test()
{
    DirectoryInfo from = new DirectoryInfo(@"C:\Test");
    using (var zipToOpen = new FileStream(@"Test.zip", FileMode.Create))
    {
        using (var archive = new ZipArchive(zipToOpen, ZipArchiveMode.Create))
        {
            foreach (var file in from.AllFilesAndFolders().OfType<FileInfo>())
            {
                var relPath = file.FullName.Substring(from.FullName.Length+1);
                ZipArchiveEntry readmeEntry = archive.CreateEntryFromFile(file.FullName, relPath);
            }
        }
    }
}

Folders don't need to be "created" in the zip-archive. The second parameter "entryName" in CreateEntryFromFile should be a relative path, and when unpacking the zip-file the directories of the relative paths will be detected and created.