Web API custom validation to check string against list of approved values

I'd like to validate an input on a Web API REST command. I'd like it to work something like State below being decorated with an attribute that limits the valid values for the parameter.

public class Item {
    ...

    // I want State to only be one of "New", "Used", or "Unknown"
    [Required]
    [ValidValues({"New", "Used", "Unknown"})]
    public string State { get; set; }

    [Required]
    public string Description { get; set; }

    ...
}

Is there a way to do this without going against the grain of Web API. Ideally the approach would be similar to Ruby on Rails' custom validation.