用于检查资格的嵌套 If 语句

Question

所以我对 C# 很陌生，在学习了一些基础知识后，我尝试制作一个简单的程序来使用 if 语句检查某人的资格。 该计划要求提供 3 项内容：年龄、身高和大学学位 您必须是 18 才能参加下一个问题，并且您必须高于 160 厘米 才能参加 CollegeDegree 问题。

现在程序运行良好，但是看它，我意识到有很多嵌套的 if 语句，代码很乱，不可读。

我需要怎么做才能让它更干净？我尝试按以下方式进行操作

if
else
if
else

但是，这会导致问题，如果第一个条件不满足，那么年龄小于 18 岁，它只会运行下一个 if 语句，而不是让用户不合格。

当前代码：

static void Main(string[] args)
        {
            int ageInput;
            int heightInput;
            bool hasCollegeDegree;
            
            
            Console.WriteLine("How old are you?");
            ageInput = Convert.ToInt32(Console.ReadLine());

            if (ageInput >= 18)
            {
                Console.WriteLine("You are older than 18");
                
                Console.WriteLine("How tall are you?");
                heightInput = Convert.ToInt32(Console.ReadLine());
                if (heightInput >= 160)
                {
                    Console.WriteLine("You are taller than 160cm");
                    
                    Console.WriteLine("Do you have a college degree?");
                    hasCollegeDegree = Convert.ToBoolean(Console.ReadLine());
                    if (hasCollegeDegree == true)
                    {
                        Console.WriteLine("You have a college degree");
                        Console.WriteLine("You are eligible");
                    }
                    else
                    {
                        Console.WriteLine("No College Degree");
                        Console.WriteLine("You are ineligible");
                    }
                }
                else
                {
                    Console.WriteLine("You are too short");
                }
            }
            else
            {
                Console.WriteLine("You are too young");
            }
        }

Answer 1

您可以使用反向条件退出代码。示例：

Console.WriteLine("How old are you?");
int ageInput = Convert.ToInt32(Console.ReadLine());
if (ageInput < 18)
{
    Console.WriteLine("You are too young");
    return;
}

Console.WriteLine("You are older than 18");

Console.WriteLine("How tall are you?");
int heightInput = Convert.ToInt32(Console.ReadLine());
if (heightInput < 160)
{
    Console.WriteLine("You are too short");
    return;
}

Console.WriteLine("You are taller than 160cm");

Console.WriteLine("Do you have a college degree?");
bool hasCollegeDegree = Convert.ToBoolean(Console.ReadLine());
if (!hasCollegeDegree)
{
    Console.WriteLine("No College Degree");
    Console.WriteLine("You are ineligible");
    return;
}

Console.WriteLine("You have a college degree");
Console.WriteLine("You are eligible");

Answer 2

我建议提取方法读取整数：

private static int ReadInteger(string question) {
  while (true) {
    if (!string.IsNullOrWhiteSpace(question))
      Console.WriteLine(question);

    if (int.TryParse(Console.ReadLine(), out int result))
      return result;

    Console.WriteLine("Sorry, not a valid integer; please, try again.");
  }
}

和布尔值：

private static HashSet<string> s_Yes = 
  new HashSet<string>(StringComparer.OrdinalIgnoreCase) {
    "Y", "Yes", "T", "True", "OK"
};

private static HashSet<string> s_No = 
  new HashSet<string>(StringComparer.OrdinalIgnoreCase) {
    "N", "No", "F", "False"
};

private static bool ReadBoolean(string question) {
  while (true) {
    if (!string.IsNullOrWhiteSpace(question))
      Console.WriteLine(question);

    string input = Console.ReadLine().Trim();

    if (s_Yes.Contains(input))
      return true;
    if (s_No.Contains(input))
      return false;

    Console.WriteLine("Sorry, not a valid value; please, try again.");
  }
}

那么你就可以放

if (ReadInteger("How old are you?") < 18) {
  Console.WriteLine("You are too young");

  return;
}

Console.WriteLine("You are older than 18");

if (ReadInteger("How tall are you?") < 160) {
  Console.WriteLine("You are too short");

  return;
}

Console.WriteLine("You are taller than 160cm");  
                
if (!ReadBoolean("Do you have a college degree (Y/N)?")) {
  Console.WriteLine("No College Degree");
  Console.WriteLine("You are ineligible");  

  return;  
}

Console.WriteLine("You have a college degree");
Console.WriteLine("You are eligible");

Answer 3

到目前为止，使用return 的答案的一个缺点是该方法已退出，因此您不能在同一方法中使用低于该点的任何代码。

另一种方法是使用 COMPOUND 布尔语句并将所有条件组合成一个布尔表达式：

if (ageInput >= 18 && heightInput >= 160 && hasCollegeDegree) 
{
    Console.WriteLine("Congratulations! You meet the criteria.");
}
else
{
    Console.WriteLine("You do not meet the criteria.");
}

如果您有许多不同的组合需要检查，这种检查方式可能会很有用。因此，用户预先输入所有信息，然后您可以进行一系列不同的复合检查，以查看他们满足哪些组合。也许您正在检查用户有资格获得列表中的哪些授权。

有关&&、|| 和! 的更多信息，请参阅Boolean logical operators。