Radajaxpanel and RegisterStartupScript

If you want call javascript from server side while using RadAjaxPanel use 
ResponseScripts.Add method. 

//Doesnt work  :
   ScriptManager.RegisterStartupScript(this, GetType(), "RefreshDD", 
"RefreshDD();", true); 

//Works :
   pnlMain.ResponseScripts.Add("RefreshDD();");