public class Album
{
public int Id { get; set; }
[Required(ErrorMessage = "Artist is required")]
[MaxLength(30)]
public string Artist { get; set; }
[Required(ErrorMessage = "Title is required")]
[MaxLength(40)]
public string Title { get; set; }
[Range(0, 10, ErrorMessage = "Rating in the range of 0-10 is required.")]
public int Rating { get; set; }
}

public class AlbumController : ApiController
{
public HttpResponseMessage Post(Album album)
{
if (!ModelState.IsValid)
{
throw new HttpResponseException(Request.CreateErrorResponse(HttpStatusCode.BadRequest,
ModelState));
}
//omitted for brevity
}
}

public class Album : IValidatableObject
{
public int Id { get; set; }
[Required(ErrorMessage = "Artist is required")]
[MaxLength(30)]
public string Artist { get; set; }
[Required(ErrorMessage = "Title is required")]
[MaxLength(40)]
public string Title { get; set; }
public int? Rating { get; set; }
public bool? Starred { get; set; }
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
if (!(Rating.HasValue && Rating > 0 && Rating < 10) || (Starred.HasValue && Starred.Value))
{
yield return new ValidationResult("You must set either the Rating in the 0-9 range or
Starred flag.");
}
}
}