Hi, ALL:<BR> I try to use server.execute() inside my page(I called PageA),Then on the buttonClick event, I try to server.execute to pageA follow by quertstring.Because querystring value,on PageA it will load usercontrol,but It always told me invalid casting exception. I use ctype(ControlName,string) to case value then use page.loadControl(ControlName) but still same error.I check my userControl, It has no outputcache and also className is right.<BR>What reason for these problem ?<BR><BR>Thanks