大家帮我看下,用这个代码下载rar文件后不能使用?

Question

public  void StartDownLoad()
        {
            /*
             * 设置按钮状态为不启用
             */
            btnLogin.Enabled = false; 
            /*
             * 定义网络路径
             */
            string url = "http://127.0.0.1/test.rar";
            /*
             * 定义保存路径
             */
            int index = url.LastIndexOf("/");
            string path = "d:\\"+url.Substring(index);
            try
            {
                HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(url);
                myRequest.Method = "GET";
                myRequest.ContentType = "application/x-www-form-urlencoded";
                HttpWebResponse wr = (HttpWebResponse)myRequest.GetResponse();
                Stream sIn = wr.GetResponseStream();
                FileStream fs = new FileStream(path, FileMode.Create, FileAccess.Write);
                long length = wr.ContentLength;
                long i = 0;
                while (i < length)
                {
                    byte[] buffer = new byte[1024];
                    i += sIn.Read(buffer, 0, buffer.Length);
                    fs.Write(buffer, 0, buffer.Length);
                    if ((i % 1024) == 0)
                    {
                        status.Text = "正在下载:" + i  + "/" + length.ToString();                    }
                    else
                    {
                        status.Text = "正在下载:" + i  + "/" + length .ToString();
                    }
                }
                
                if (i == length)
                {
                    MessageBox.Show("下载完成!");
                    StreamWriter writeTxt = new StreamWriter(txt,false,Encoding.Default);
                    writeTxt.Write(version);
                    writeTxt.Flush();
                    writeTxt.Close();
                    fs.Close();
                    sIn.Close();
                    wr.Close();
     
                    btnLogin.Enabled = true;
                    demoThread.Abort();                }            }
                
            
            catch(WebException ex)
                {
                    MessageBox.Show(ex.Message);
                    status.Text = "";
                }                
            }
下载完成后不能打开压缩文件