c# - How I can control a ArrayList for duplicate value? -

i have arraylist string(codes) , want control whether string duplicate in arraylist. if string duplicate want other code arraylist.

my code:

private void btn_create_click(object sender, eventargs e) {     arraylist list = new arraylist();      try     {         list = dodeserialize();      }     catch (exception ex)     {         lbl_status.text = ex.message;      }      string code = getcode(7);      code = "2 - " + code;      int test = list.indexof(code);       txt_code.text = code;     lbl_status.text = "code wurde erstellt";       list.add(code);      doserialize(list); } 

add in place of list.add(code);. method checks whether item in array list.

if(!list.contains(code)) {     // code not exist in list, add     list.add(code); } else {     // code exists, here. } 

see here more information list<t>.contains() method.