Question

我有以下代码，但是当我进入＆＃34; 12＆＃34;我仍然得到了＃34;你是一个老人＆＃34;。不是9 - 15，数字9到15？如何用一个案例处理多个值？

  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;
  }

Answer 1

1 - 8 = -7

9 - 15 = -6

16 - 100 = -84

你有：

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

使用：

case 1:
case 2: 
case 3:

等，或（可能更具可读性）使用：

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

等

Answer 2

您必须执行以下操作：

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

Answer 3

您无法在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;

...........等

Answer 4

你可以改用ifelse。但如果你想知道如何在这种情况下使用开关。这是一个例子。

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;
}

希望有所帮助！：）

Answer 5

在C＃7中，可以使用when clause in a case statement。

ng build --prod --extract-css=false

Answer 6

你可以试试这个。

switch (Valor)
            {
                case (Valor1 & Valor2):

                    break;               
            }

Answer 7

无法在一个“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）或调用一个方法来计算整数所属的范围并返回表示该范围的值（例如“minor”，“adult”等），然后在switch语句中计算此返回值。当然，你可能仍然在自定义方法中使用if语句。

Answer 8

将年龄的业务规则与操作分开，例如（仅输入NB，未选中）

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");
}

`

Answer 9

那呢？

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;
}

欢呼

Answer 10

在 C# 8.0 中，您可以使用适合您情况的 switch expression 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);

开关：一种情况下有多个值？

10 个答案: