public delegate void DelegateProgress();

  DelegateProgress Press = new DelegateProgress(MyFunction);
  IAsyncResult result = team_Press.BeginInvoke(null, null);
  ...
  protected void MyFunction()
  {
     ...
  }

/// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="originalImagePath">源图路径（物理路径）</param>
        /// <param name="thumbnailPath">缩略图路径（物理路径