很急 `` 给为高手帮帮忙啊!小弟真的很急 一个很简单的问题 被我想的不知道为什么弄了啊!

Question

                     显示让用户在这里输入"y 或者 n "
                Console.SetCursorPosition(24, 15);
                //判断这为学生是否想继续借书 定义一个变量来接受用户的选择                string OOO = Console.ReadLine();
                if (OOO == "Y" && OOO == "y")
                {
                    
                    Console.WriteLine("\n\n\n\t\t\tWelcome cunturn borrow books");
                    Console.WriteLine("\n\n\n\t\t\t请输入借书的数量");
                    string num = Console.ReadLine();
                    //判断学生借的是基本书
                    if (num == "4")
                    {
                        string book1, book2, book3, book4;
                        Thread.Sleep(1000);
                        Console.WriteLine("欢迎四书系统");
                        book1 = Console.ReadLine();
                        book2 = Console.ReadLine();
                        book3 = Console.ReadLine();
                        book4 = Console.ReadLine();                        Console.WriteLine("{0},{1},{2},{3}", book1, book2, book3, book4);                        
                      }                       else if (num == "3")
                         {
                           string book1, book2, book3;
                           Console.WriteLine("欢迎三书系统");
                           book1 = Console.ReadLine();
                           book2 = Console.ReadLine();
                           book3 = Console.ReadLine();
                           //接受三本书的名字　　进行插入数据库
                         }
                      else if (num == "2")
                       {
                           string book1, book2;
                           Console.WriteLine("欢迎两书系统");
                           book1 = Console.ReadLine();
                           book2 = Console.ReadLine();
                          //接受两本书的名字　进行插入数据库
                       }
                       else if (num == "1")
                         {
                           string book1;
                           Console.WriteLine("欢迎一书系统");
                           book1 = Console.ReadLine();
                            //接受一本书的名字　　进行插入数据库
                         }
                       else
                         {
                           Console.WriteLine("你输入的这个值不在要求范围之内");
                         }
                       }这上面的代码已经在if语句中了为什么 就是不把接受了用户的值之后的一个判断用起来呢!很很急 帮帮忙!

Answer 1

设置断点，然后单步调试一下，看OOO和num的值是什么。

Answer 2

 if (OOO == "Y" && OOO == "y") 
???

Answer 3

OOO == "Y" && OOO == "y"?
怎么可能你输入的既是Y又是y？

Answer 4

     if (OOO == "Y" || OOO == "y") 

Answer 5

最好的写法就是if(string.Compare(OOO,"y",true) == 0)

Answer 6

if (OOO == "Y" && OOO == "y") 
是不是应该是if (OOO == "Y" || OOO == "y") ？

Answer 7

if(string.Compare(OOO.trim(),"y",true) == 0)

Answer 8

 if (OOO == "Y" && OOO == "y")
这句有问题，应该是：
 if (OOO == "Y" || OOO == "y")