Question

更新：

有没有办法完成下面的代码尝试做的事情（不通过语法，因为案例2和案例3不能有重复的声明和/或因为num不能同时为2和3 ）？

        var num = 0;
        switch (num)
        {
            case 1:
                //do stuff applicable to 1 only;
                break;
            case 2:
                //do stuff applicable to 2 only;
                break;
            case 3:
                //do stuff applicable to 3 only;
                break;
            case 2:
            case 3:
                //do stuff applicable to 2 and 3 only;
                break;
        }

Answer 1

这个问题令人困惑。我认为你想要的是一个运行两个的案例，一个运行三个的案例，一个运行两个或三个的案例。

只需使用两个开关：

    switch (num)
    {
        case 1: One(); break;
        case 2: Two(); break;
        case 3: Three(); break;
    }
    switch (num)
    {
        case 2:
        case 3: TwoOrThree(); break;
    }

或者

    switch (num)
    {
        case 1: One(); break;
        case 2:
        case 3: 
          switch (num)
          {
            case 2: Two(); break;
            case 3: Three(); break;
          }
          TwoOrThree();
          break;
    }

或复制代码：

    switch (num)
    {
        case 1: One(); break;
        case 2: Two(); TwoOrThree(); break;
        case 3: Three(); TwoOrThree(); break;
    }

我不建议像这样重复代码：

    switch (num)
    {
        case 1: One(); break;
        case 2: Two(); goto twoOrThree; break;
        case 3: Three(); twoOrThree: TwoOrThree(); break;
    }

呸。

Answer 2

不是单级switch（或令人讨厌的GOTO）。一个开关只能执行一个案例。在2/3案例中，更好的解决方案是嵌套if（或switch）：

switch (num)
{
    case 1:
        //do stuff applicable to 1 only
        break;
    case 2:
    case 3:
        if(num == 2)
        {
            //do stuff applicable to 2 only
        }
        if(num == 3)
        {
            //do stuff applicable to 3 only
        }
        //do stuff applicable to 2 OR 3
        break;
}

Answer 3

就这么简单......

switch (value)
{
    case 1:
        // Do 1 stuff
        break;
    case 2:
    case 3:
        // We can use an if-else construct here given that there's only two possibilities.
        if (value == 2)
        {
            // 2 only stuff here
        }
        else
        {
            // 3 only stuff here
        }

        // Do anything applicable to BOTH here, or above the if construct, depending on your requirements.

        break;
    default:
        // Any other stuff here
        break;
}

或者只使用if构造，它可以说更清晰（切换实际上仅用于简单的多对一逻辑映射）...

if (value == 1)
{
    // 1 stuff
}
else if (value == 2 || value == 3)
{
    if (value == 2) {
        // 2 stuff only
    }
    else
    {
        // 3 stuff only
    }

    // 2 or 3 stuff, or above the if construct above, if you require.
}
else
{
    // Anything else here
}

或者只是......

switch (value)
{
    case 1:
        OneStuff();
        break;
    case 2:
        TwoStuff();
        TwoOrThreeStuff();
        break;
    case 3:
        ThreeStuff();
        TwoOrThreeStuff();
        break;
    default:
        AnythingElse();
}

用不同的方法包装你需要做的每件事。

第三种方法是我的偏好。它比使用开关的复杂混合物更简洁，更容易调试。

Answer 4

您只能使用if语句

var num = 0;
if(num == 1)
{
    // do stuff applicable to 1 only
}
else if(num == 2)
{
    // do stuff applicable to 2 only
}
else if(num == 3)
{
    // do stuff applicable to 3 only
}
if(num == 2 || num == 3)
{
    // do stuff applicable to 2 AND 3
}

或switch和if

switch (num)
{
    case 1: 
        // do stuff applicable to 1 only
        break;
    case 2: 
        // do stuff applicable to 2 only
        break;
    case 3: 
        // do stuff applicable to 3 only
        break;
}
if(num == 2 || num == 3)
{
    // do stuff applicable to 2 AND 3
}

Answer 5

您可以使用goto case语句，并在案例2和3中为组合操作设置唯一标识符。请确保它永远不会被任何其他数字命中：

var num = 0;
var text = "";
switch (num)
{
    case 1:
        text = "do stuff applicable to 1 only";
        break;
    case 2:
        text = "do stuff applicable to 2 only";
        goto case 23;
    case 3:
        text = "do stuff applicable to 3 only";
        goto case 23;
    case 23:
        text = "do stuff applicable to 2 AND 3";
        break;
}

一般不建议使用goto，但通常在switch语句和类似的情况下使用它。

C＃Switch语句场景

5 个答案: