c# - 开关：一种情况下有多个值？

Question

我有以下一段代码，但是当我输入“12”时，我仍然得到“你是个老人”。9 - 15 不是 9 到 15 的数字吗？我如何在一种情况下处理多个值？

  int age = Convert.ToInt32(txtBoxAge.Text);

  switch (age) 

  {
    case 1 - 8:
  MessageBox.Show("You are only " + age + " years old\n You must be kidding right.\nPlease fill in your *real* age.");
    break;
    case 9 - 15:
  MessageBox.Show("You are only " + age + " years old\n That's too young!");
    break;
    case 16-100:
  MessageBox.Show("You are " + age + " years old\n Perfect.");
    break;
    default:
  MessageBox.Show("You an old person.");
    break;
  }

score 41 · Accepted Answer

1 - 8 = -7

9 - 15 = -6

16 - 100 = -84

你有：

case -7:
    ...
    break;
case -6:
    ...
    break;
case -84:
    ...
    break;

要么使用：

case 1:
case 2: 
case 3:

等，或者（也许更易读）使用：

if(age >= 1 && age <= 8) {
     ...
} else if (age >= 9 && age <= 15) {
     ...
} else if (age >= 16 && age <= 100) {
     ...
} else {
     ...
}

ETC

score 35 · Accepted Answer

35

您必须执行以下操作：

case 1:
case 2:
case 3:
//do stuff
break;

于 2012-10-16T09:40:38.993 回答

score 8 · Accepted Answer

您不能在 case 语句中指定范围，可以执行以下操作。

case 1:
case 2:
case 3:
case 4:
case 5:
case 6:
case 7:
case 8:
   MessageBox.Show("You are only " + age + " years old\n You must be kidding right.\nPlease fill in your *real* age.");
break;

case 9:
case 10:
case 11:
case 12:
case 13:
case 14:
case 15:
   MessageBox.Show("You are only " + age + " years old\n That's too young!");
   break;

...........ETC。

score 8 · Accepted Answer

在 C# 7 中，可以在 case 语句中使用 when 子句。

int age = 12;
switch (age) 
{
  case int i when i >=1 && i <= 8:
    System.Console.WriteLine("You are only " + age + " years old. You must be kidding right. Please fill in your *real* age.");
    break;
  case int i when i >=9 && i <= 15:
    System.Console.WriteLine("You are only " + age + " years old. That's too young!");
    break;
  case int i when i >=16 && i <= 100:
    System.Console.WriteLine("You are " + age + " years old. Perfect.");
    break;
  default:
    System.Console.WriteLine("You an old person.");
    break;
}

score 5 · Accepted Answer

您可以使用 ifelse 代替。但是如果您想知道在这种情况下如何使用 switch。这里是一个示例。

int age = Convert.ToInt32(txtBoxAge.Text);`
int flag;
if(age >= 1 && age <= 8) {
flag = 1;
} else if (age >= 9 && age <= 15) {
 flag = 2;
} else if (age >= 16 && age <= 100) {
 flag = 3;
} else {
 flag = 4;   
}
switch (flag) 

{
 case 1:
  MessageBox.Show("You are only " + age + " years old\n You must be kidding right.\nPlease fill in your *real* age.");
break;
case 2:
  MessageBox.Show("You are only " + age + " years old\n That's too young!");
break;
case 3:
  MessageBox.Show("You are " + age + " years old\n Perfect.");
break;
default:
  MessageBox.Show("You an old person.");
break;
}

希望有帮助！:)

score 2 · Accepted Answer

C# 8.0您可以使用适合您情况的switch表达式语法。

int age = Convert.ToInt32(txtBoxAge.Text);

string message = age switch
{
    >= 1 and <= 8 => $"You are only {age} years old\n You must be kidding right.\nPlease fill in your *real* age.",
    >= 9 and <= 15 => $"You are only {age} years old\n That's too young!",
    >= 16 and <= 100 => $"You are {age} years old\n Perfect.",
    _ => "You an old person.",
};

MessageBox.Show(message);

score 0 · Accepted Answer

你可以试试这个。

开关（勇气）
            {
                案例（Valor1 和 Valor2）：

                    休息;               
            }

score 0 · Accepted Answer

没有办法在一个“案例”中评估多个值。您可以使用 if 语句（如其他人所建议的那样）或调用一个方法来评估整数所属的范围并返回一个表示该范围的值（例如“minor”、“adult”等），然后在 switch 语句中评估这个返回值。当然，您可能仍在自定义方法中使用 if 语句。

score 0 · Accepted Answer

将年龄的业务规则与操作分开，例如（NB 只是输入，未检查）

enum eAgerange { eChild, eYouth, eAdult, eAncient};
eAgeRange ar;
if(age <= 8) ar = eChild;
else if(age <= 15) ar = eYouth;
else if(age <= 100) ar = eAdult;
else ar = eAncient;
switch(ar)
{
 case eChild: 
     // action
 case eYouth:
     // action
 case eAdult:
     // action
 case eAncient:
     // action
 default: throw new NotImplementedException($"Oops {ar.ToString()} not handled");
}

`

score 0 · Accepted Answer

那这个呢？

switch (true) 
{
    case (age >= 1 && age <= 8):
        MessageBox.Show("You are only " + age + " years old\n You must be kidding right.\nPlease fill in your *real* age.");
    break;
    case (age >= 9 && age <= 15):
        MessageBox.Show("You are only " + age + " years old\n That's too young!");
    break;
    case (age >= 16 && age <= 100):
        MessageBox.Show("You are " + age + " years old\n Perfect.");
    break;
    default:
        MessageBox.Show("You an old person.");
    break;
}

干杯

c# - 开关：一种情况下有多个值？

10 回答 10

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