Zip and Unzip from a C# program using J# runtime

using ICSharpCode.SharpZipLib.Zip;

/// <summary>
/// Packs a folder and all files in all its subfolders into a ZIP file preserving the relative paths
/// Requires ICSharpCode.SharpZipLib library
/// http://www.icsharpcode.net/OpenSource/SharpZipLib
/// </summary>
static public void PackFolderIntoZipFile(string s_Folder, string s_ZipFile)
{
	ZipOutputStream i_zStream = new ZipOutputStream(File.Create(s_ZipFile));
	i_zStream.SetLevel(5); // Compression level (0-9)

	int s32_BaseFolderLen = s_Folder.Length;
	if (s_Folder.Substring(s_Folder.Length-1) != "\\") s32_BaseFolderLen ++;

	ArrayList i_FileList = new ArrayList();
	EnumFiles(ref i_FileList, s_Folder, "*.*", true);

	Byte[] u8_Buf = new Byte[0x100000]; // 1 Megabyte buffer

	foreach (string s_File in i_FileList)
	{
		FileStream i_fStream = null;
		// Catch errors of files which are locked (cannot be opened)
		try   { i_fStream = File.OpenRead(s_File); }
		catch { continue; }

		// Cut the base folder ("E:\ZipFolder\Subfolder\File.txt" -> "Subfolder/File.txt")
		// The zip archive requires "/" as separator
		string s_ZipPath = s_File.Substring(s32_BaseFolderLen).Replace("\\", "/");

		ZipEntry i_ZipEntr = new ZipEntry(s_ZipPath);
		FileInfo i_Info    = new FileInfo(s_File);
		i_ZipEntr.DateTime = i_Info.LastWriteTime;
		i_zStream.PutNextEntry(i_ZipEntr);

		while (true)
		{
			int s32_Len = i_fStream.Read(u8_Buf, 0, u8_Buf.Length);
			if (s32_Len <= 0)
				break;
			
			i_zStream.Write(u8_Buf, 0, s32_Len);
		}

		i_fStream.Close();
	}

	i_zStream.Finish();
	i_zStream.Close();
}

/// <summary>
/// This recursive function searches all files in the given folder and its subfolders
/// s_Filter = "*.Extension"
/// s_Path   = Start path
/// </summary>
static public void EnumFiles(ref ArrayList i_FileList, string s_Path, string s_Filter, bool b_Subfolders)
{
	if (s_Path == null || s_Path == "")
		return;

	string[] s_Files = Directory.GetFiles(s_Path, s_Filter.Trim());
	foreach (string s_File in s_Files)
	{
		i_FileList.Add(s_File);
	}

	if (b_Subfolders)
	{
		string[] s_Dirs = Directory.GetDirectories(s_Path);
		foreach (string s_Dir in s_Dirs)
		{
			EnumFiles(ref i_FileList, s_Dir, s_Filter, true);
		}
	}
}