public User(string firstName, string lastName, string email, DateTime?lastModified = null)
{
if (StringExtensions.AnyNullOrWhiteSpace(firstName, lastName, email))
{
throw new ArgumentNullException("All arguments must not be null or whitespace.");
}
FirstName = firstName;
LastName = lastName;
Email = email;
LastModified = lastModified ?? DateTime.Now;
}
