viewstate 記錄多項紀錄

有2个button, 分别叫button1,button2.
当我按一下button1,储存"1"在viewstate["record"],
当我按一下button2,储存"2"在viewstate["record"],
例如button1>button2>button1>button1
最终viewstate["record"]储存了["1","2","1","1"]

我想问要实现上面所说的情况,c#如何写?

补充：.NET技术 ,  ASP.NET