public IPerson FindByUsername(string username)
{
if (username == null)
{
throw new ArgumentException();
}
var newPerson = PersonList.FirstOrDefault(p => p.Username == username);
if (newPerson == null)
{
throw new InvalidOperationException();
}
return(newPerson);
}
public IPerson FindById(int id)
{
if (id < 0)
{
throw new ArgumentOutOfRangeException();
}
var newPerson = PersonList.FirstOrDefault(p => p.Id == id);
if (newPerson == null)
{
throw new InvalidOperationException();
}
return(newPerson);
}