public MemberInfo Login(MemberUdt member)
 {
     return(BookStoreException.TryThrow <MemberInfo>(() =>
     {
         return new MemberInfo();
     }));
 }
 public IEnumerable <Book> GetBooks()
 {
     return(BookStoreException.TryThrow(() =>
     {
         return Enumerable.Range(1, 500).Select(item => new Book {
         });
     }));
 }