C#中IF语句添加多条件时出现编译错误求助

问题描述 #

我写了一个用于检查用户是否符合俱乐部入场年龄的小程序，同时要在未成年场次时判断用户年龄是否合适或超龄，但出现了以下编译错误：

Compilation error (line 19, col 20): ) expected
Compilation error (line 19, col 87): ; expected
Compilation error (line 19, col 87): } expected
Compilation error (line 21, col 4): 'else' cannot start a statement.
Compilation error (line 21, col 4): Syntax error, '(' expected
Compilation error (line 21, col 4): Invalid expression term 'else'
Compilation error (line 21, col 4): ) expected
Compilation error (line 21, col 4): Invalid expression term 'else'
Compilation error (line 21, col 4): ; expected
Compilation error (line 19, col 12): 'bool' is a type, which is not valid in the given context

我已经检查了分号、括号和大括号，但还是搞不懂问题出在哪，以下是我的代码：

using System;
                    
public class Program
{
    public static void Main()
    {
        int clubAgeMin = 18;
        int clubUAgeMin =(clubAgeMin - 2);
        int clubUAgeMax =17;
        int userAge =20;
        Boolean isUNight =false;
        
        if (userAge >= clubAgeMin && isUNight == false) {
        Console.WriteLine("Welcome to the club!"); 
        }
        else if (userAge < clubAgeMin && isUNight == false) {
        Console.WriteLine("Sorry but your under 18, please come back when we have a underage's night"); 
        }
        else if (Boolean isUNight == true && userAge >= clubUAgeMin && userAge < clubUAgeMax) {
        Console.WriteLine("Wlcome to the club's underage night!");
        }
        else if (userAge > clubUAgeMax) {
        Console.WriteLine("Sorry buddy but your too old for the underage night");
        }
        else if (userAge < clubUAgeMin) {
        Console.WriteLine("Sorry buddy but your too young for the underage night, comeback when you are older");
        }
        
    }
}

错误原因分析 #

• 核心语法错误：第19行的else if条件中，错误地给变量isUNight添加了类型声明Boolean。在条件表达式里，直接使用已声明的变量即可，不需要重复指定类型。另外，布尔值判断可以简化，isUNight == true直接写成isUNight更符合C#编码规范。
• 拼写错误：代码里存在几处拼写问题，比如your应改为you're（表示"你是"），Wlcome应为Welcome，comeback应拆分为come back。
• 逻辑漏洞：部分未成年场次的分支没有判断isUNight是否为true，可能导致逻辑混乱；同时userAge < clubUAgeMax应该改为userAge <= clubUAgeMax，因为clubUAgeMax是17，应该允许17岁用户入场。

修正后的代码 #

using System;
                    
public class Program
{
    public static void Main()
    {
        int clubAgeMin = 18;
        int clubUAgeMin = clubAgeMin - 2;
        int clubUAgeMax = 17;
        int userAge = 20;
        bool isUNight = false; // C#惯例使用小写bool
        
        if (userAge >= clubAgeMin && !isUNight) {
            Console.WriteLine("Welcome to the club!"); 
        }
        else if (userAge < clubAgeMin && !isUNight) {
            Console.WriteLine("Sorry but you're under 18, please come back when we have an underage's night"); 
        }
        else if (isUNight && userAge >= clubUAgeMin && userAge <= clubUAgeMax) {
            Console.WriteLine("Welcome to the club's underage night!");
        }
        else if (isUNight && userAge > clubUAgeMax) {
            Console.WriteLine("Sorry buddy but you're too old for the underage night");
        }
        else if (isUNight && userAge < clubUAgeMin) {
            Console.WriteLine("Sorry buddy but you're too young for the underage night, come back when you are older");
        }
    }
}

内容的提问来源于stack exchange，提问作者Dima