c# - How to add list into list with some condition? -

so if have this:

public mainmenumodel(string transkey, string statename, string displayurl, bool hassubmenu= false,list<submenumodel>submenu=null) {             transkey = transkey;             statename = statename;             displayurl = displayurl;                       hassubmenu = hassubmenu;             submenu = submenu;              }         public string transkey { get; set; }         public string statename { get; set; }         public string displayurl { get; set; }          public bool hassubmenu { get; set; }          public list<submenumodel>submenu { get; set; }  }    public class submenumodel {             public submenumodel(string transkey, string statename, string displayurl)             {                 transkey = transkey;                 statename = statename;                 displayurl = displayurl;                           }             public string transkey { get; set; }             public string statename { get; set; }             public string displayurl { get; set; }   } 

how can add submenu in mainmenu condition example:

if(test!=null) {     submenu.add(new submenumodel("personal_information","account.personalinformation","/account/personalinformation")); } submenu.add(new submenumodel("notifications", "account.notificationsettings", "/account/notifications")); submenu.add(new submenumodel("change_password", "account.changepassword", "/account/passwordchange")); submenu.add(new submenumodel("game_settings", "default", "default")); 

mainmenu.add(submenu) --> not working...how can add condition sub menu in main menu? tried mainmenu.addrange(submenu) cant because different types. tried :

for (int = 0; < submenu.count; i++) {    mainmenu[0].submenu.add(submenu[i]); } 

but error.any suggestion?

because in mainmenumodel have

public list<submenumodel> submenu { get; set; } 

so, this

mainmenu[positionofdatainlist].submenu = submenutoadd; 

if have more submenu add do

mainmenu[positionofdatainlist].submenu.addrange(anothersubmenu);