Unable use RegisterStartupScript inside an update panel on "onclick" event

Problem


One Update panel with one gridview in it, and one button on header.

update Panel =update1  
gridview="gridview1" ,
one button in header=btnAdd
 





An javascript alert is needed when user clicks btnAdd_click




Solution : 


ScriptManager.RegisterStartupScript(gridview1, gridview1.GetType(), "edit", "alert('xx')", true);