public static bool Login(string username, string password)
 {
     if (username == "user")
     {
         PersistanceUtil.SetValueByKey(PersistanceUtil.Keys.Username.ToString(), username);
         return(true);
     }
     return(false);
 }
 public static bool IsLoggedIn() => PersistanceUtil.HasKey(PersistanceUtil.Keys.Username.ToString());
 public static bool Logout()
 {
     PersistanceUtil.RemoveKey(PersistanceUtil.Keys.Username.ToString());
     return(true);
 }