易错问题汇总

• "KY1" & "□□".Substring(0, 2) ==> "KY□□" (先取前两位,后连接"□□")
  

       正确为:     ("KY1" & "□□").Substring(0, 2) ==> "KY"  (防止字符串为null时,取前两位出错)