Say I have a model like this:
public class Person
{
public int Id {get; set}
public int Username {get; set;}
//...other props
}
For a POST method, how can model state validation be used to ensure that a given username is not already used? Surely it will require a database lookup, but what is a simple, clean pattern for achieving this?
Second question: how can the same be achieved in a PUT method, where the lookup logic should ignore the one record that is being updated, since it obviously exists in the DB?
