C# WinForm 文件上传下载

/// <summary>
  /// WebClient上传文件至服务器
  /// </summary>
  /// <param name="fileNamePath">文件名，全路径格式</param>
  /// <param name="uriString">服务器文件夹路径</param>
  private void UpLoadFile(string fileNamePath,string uriString)
  {
   string fileName = fileNamePath.Substring(fileNamePath.LastIndexOf("\\") + 1);
   NewFileName = DateTime.Now.ToString("yyMMddhhmmss") + DateTime.Now.Millisecond.ToString() + fileNamePath.Substring(fileNamePath.LastIndexOf(".")); 
   string fileNameExt = fileName.Substring(fileName.LastIndexOf(".") + 1);
   if(uriString.EndsWith("/") == false) uriString = uriString + "/";

   uriString = uriString + NewFileName;
   /// 创建WebClient实例
   WebClient myWebClient = new WebClient();
   myWebClient.Credentials = CredentialCache.DefaultCredentials;

   // 要上传的文件
   FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
   //FileStream fs = OpenFile();
   BinaryReader r = new BinaryReader(fs);
   try
   {
    //使用UploadFile方法可以用下面的格式
    //myWebClient.UploadFile(uriString,"PUT",fileNamePath);
    byte[] postArray = r.ReadBytes((int)fs.Length);
    Stream postStream = myWebClient.OpenWrite(uriString,"PUT");
    if(postStream.CanWrite)
    {
     postStream.Write(postArray,0,postArray.Length);
    }
    else
    {
     AppHelper.MessageService.ShowError("文件目前不可写！");
    }
    postStream.Close();
   }
   catch
   {
    AppHelper.MessageService.ShowError("文件上传失败，请稍候重试~");
   }
  }


  /// <summary>
  /// 下载服务器文件至客户端

  /// </summary>
  /// <param name="URL">被下载的文件地址，绝对路径</param>
  /// <param name="Dir">另存放的目录</param>
  public void Download(string URL,string Dir)
  {
   WebClient client = new WebClient();
   string fileName = URL.Substring(URL.LastIndexOf("\\") + 1);  //被下载的文件名

   string Path = Dir+fileName;   //另存为的绝对路径＋文件名
   
   try
   {
    WebRequest myre=WebRequest.Create(URL); 
   }
   catch
   {
    //MessageBox.Show(exp.Message,"Error"); 
   }
   
   try
   {
    client.DownloadFile(URL,fileName);
    FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
    BinaryReader r = new BinaryReader(fs);
    byte[] mbyte = r.ReadBytes((int)fs.Length);

    FileStream fstr = new FileStream(Path,FileMode.OpenOrCreate,FileAccess.Write); 

    fstr.Write(mbyte,0,(int)fs.Length);
    fstr.Close(); 

   } 
   catch
   {
    //MessageBox.Show(exp.Message,"Error");
   } 
  }