// 책 가격 입력기능 public string enterBookPriceFunction() { print.enterBookPrice(); bookPrice = Console.ReadLine(); if (bookPrice == "b") { run.bookMenu(); } if (exception.bookPriceCheck(bookPrice)) { this.enterBookPriceFunction(); } else if (string.IsNullOrWhiteSpace(bookPrice)) { bookPrice = "FREE"; } return(bookPrice); }