使用C#遇到困难 [英] goto difficulties with C#

问题描述

为什么会出现以下编译器错误:

Why do I get the following compiler error:

//错误CS0159:没有这样的标签"lbl_proc_20"

//error CS0159: No such label 'lbl_proc_20'

具有以下代码:

//JUST A DUMMY CODE TO ILLUSTRATE THE CONCEPT
int a = resultOfFunction1();
int b = resultOfFunction2();

//10+ Local variables that are calculated depending on the results above

if (a < 10)
{
    switch (b)
    {
        case 0:
            //Actions for A<10, B=0, using local variables
            break;
        case 1:
            double c = someFunction(a, b);  //In real code involves calculations based on a and b
            if(c > 10.0)
                goto lbl_proc_20;   //error CS0159: No such label 'lbl_proc_20' within the scope of the goto statement

                    //Actions for A<10, B=1, using local variables
            break;
        default:
            //Actions for A<10, B=Other, using local variables
            break;
    }
}
else if (a < 20)
{
lbl_proc_20:
    switch(b)
    {
        case 0:
            //Actions for A<20, B=0, using local variables
            break;
        case 1:
            //Actions for A<20, B=1, using local variables
            break;
        case 2:
            //Actions for A<20, B=2, using local variables
            break;
        default:
            //Actions for A<20, B=Other, using local variables
            break;
    }
}
else if (a < 30)
{
    switch(b)
    {
        case 0:
            //Actions for A<30, B=0, using local variables
            break;
        case 1:
            //Actions for A<30, B=1, using local variables
            break;
        case 2:
            //Actions for A<30, B=2, using local variables
            break;
        default:
            //Actions for A<30, B=Other, using local variables
            break;
    }
}

为什么我的goto语句出错并且如何使其起作用?

Why am I getting an error for a goto statement and how to make it work?

编辑:更改了示例以说明实际代码.

Changed the sample to illustrate the actual code.

推荐答案

您只能使用goto跳转到goto范围内的标签.从文档描述了错误CS0159:

You can only use goto to jump to labels within the scope of the goto. From the docs that describes error CS0159:

在goto语句的范围内找不到goto语句引用的标签.

The label referenced by the goto statement could not be found within the scope of the goto statement.

尽管标签存在，但是您不能从if块跳入else块. else中的代码与包含goto的代码的作用域不同.

Although the label exists, you can't jump out of an if block into an else block. The code within else is not the same scope as that that contains the goto.

是时候重构代码了，所以不需要goto.

It's time to restructure your code so it doesn't need goto.

修改

您应该尝试简化逻辑.多个功能优于goto语句.

You should try to simplify your logic. Multiple functions are preferable to goto statements.

您可能要考虑的一个选项是 Windows Workflow Foundation .这是一个非常简洁的工具，可让您直观地将逻辑表示为流程图.然后，WWF将生成处理您指定的逻辑所必需的代码.这可能有用，因为它看起来就像您正在创建某种类型的有限状态机或类似过程一样.

One option you might want to consider is Windows Workflow Foundation. It's a really neat tool that lets you represent your logic visually as a flow chart. WWF will then generate the code necessary to handle the logic you specify. This might work for since it appears like you are creating some type of finite state machine or similar process.

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