http://space.itpub.net/12639172/viewspace-674866

小结：
  memorystream
  bitmap
  file
  fileupload
  save方法
 
fileupload类的详解,请见下述链接:
http://msdn.microsoft.com/zh-cn/library/system.web.ui.webcontrols.fileupload%28VS.80%29.aspx