Com base na resposta de Simon McKenzie a esta pergunta , sugiro usar um par de métodos como este:
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);
}
}