asp.net - Adding multiple custom controls -

i have custom control (customcontainer) can hold multiple custom controls of type conditioncontrol. when click button in customcontainer control want add customcontrol container.

protected void imagebutton1_click(object sender, imageclickeventargs e)         {             customcontrolspanel.controls.add(new literalcontrol("<br />"));             conditioncontrol mycc = (conditioncontrol)loadcontrol(@"~/conditioncontrol.ascx");             customcontrolspanel.controls.add(mycc);         } 

this works once. click once, adds condition control not work anymore. how can fix ?

edit: tried saving control collection of panel session variable , using in order restore controls so:

protected void page_load(object sender, eventargs e)         {             if (!page.ispostback)             {                 session["controls"] = conditioncontrolspanel.controls;             }             else             {                 controlcollection temp = (controlcollection)session["controls"];                 conditioncontrolspanel.controls.clear();                 foreach (control ctrl in temp)                 {                     conditioncontrolspanel.controls.add(ctrl);                 }              }         } 

i error when try add new control saying collection modified; enumeration operation may not execute. when try foreach

that because everytime click on button, postbacks, removes first 1 , adds new one. overcome this, can either prevent postback(by updatepanel) or keep count of added conditioncontrols (like in session) , add controls many counter keep in session says