public async Task <Organizer> CreateAsync(
[NotNull] string name,
DateTime birthDate,
[CanBeNull] string shortBio = null)
{
Check.NotNullOrWhiteSpace(name, nameof(name));
var existingOrganizer = await _organizerRepository.FindByNameAsync(name);
if (existingOrganizer != null)
{
throw new OrganizerAlreadyExistsException(name);
}
return(new Organizer(
name,
birthDate,
shortBio
));
}