public IEnumerable <ValidationResult> Validate(ValidationContext validationContext)
{
List <ValidationResult> errors = new List <ValidationResult>();
if (Actors != null && Actors.Any())
{
bool duplicates = Actors.GroupBy(a => a).Any(a => a.Count() > 1);
if (duplicates)
{
errors.Add(new ValidationResult("Duplicate actors", new[] { "Actors" }));
}
}
return(errors);
}