//ADD BOOK INTO BOOK TABLE => BL public string AddBookBL(string bookName, string bookAuthor, string bookISBN, double bookPrice, int bookCopies) { string isBookValid = BookValidate(bookName, bookAuthor, bookISBN, bookPrice, bookCopies); if (isBookValid == "true") { BookDAL bookDAL = new BookDAL(); bool isDone = bookDAL.AddBookDAL(bookName, bookAuthor, bookISBN, bookPrice, bookCopies); if (isDone != true) { return("Server error, "); } else { return("true"); } } else { return(isBookValid); } }