public static User CreateUser(string name, string userName)
{
Guard.Against.NullOrEmpty(name, nameof(name));
Guard.Against.NullOrEmpty(userName, nameof(userName));
if (UsersList.Any(c => c.UserName.ToLower() == userName.ToLower()))
{
return(UsersList.Single(c => c.UserName.ToLower() == userName.ToLower()));
}
return(new User(name, userName));
}