c# sharpziplib adding file to existing archive

Question

am trying to add a file to an existing archive using the following code. When run no errors or exceptions are shown but no files are added to the archive either. Any ideas w

Answer 1

    /// 

    /// 添加压缩文件 p 为客户端传回来的文件/夹列表,用分号隔开，不包括主路径， zipfile压缩包的名称
    /// 
    /// 
    /// 
    public void AddZipFile(string p, string zipfile)
    {
        if (ServerDir.LastIndexOf(@"\") != ServerDir.Length - 1)
        {
            ServerDir += @"\";
        }
        string[] tmp = p.Split(new char[] { ';' }); //分离文件列表
        if (zipfile != "") //压缩包名称不为空
        {
            string zipfilepath=ServerDir + zipfile;
            if (_ZipOutputStream == null)
            {
                _ZipOutputStream = new ZipOutputStream(File.Create(zipfilepath));
            }
            for (int i = 0; i < tmp.Length; i++)
            {
                if (tmp[i] != "") //分离出来的文件名不为空
                {
                    this.AddZipEntry(tmp[i], _ZipOutputStream, out _ZipOutputStream); //向压缩文件流加入内容
                }
            }
        }
    }
    private static ZipOutputStream _ZipOutputStream;
    public void Close()
    {
        _ZipOutputStream.Finish();
        _ZipOutputStream.Close();
    }