如何从PowerShell中的ForEach-Object退出 [英] How to exit from ForEach-Object in PowerShell

问题描述

我有以下代码：

  $ project.PropertyGroup | Foreach {
 if（$ _。GetAttribute（'Condition'）。Trim（）-eq $ propertyGroupConditionName.Trim（））{
 $ a = $ project.RemoveChild（$ _）; 
 Write-Host $ _。GetAttribute（'Condition'）已被删除。 
} 
}; 
  

问题＃1：如何退出ForEach？我试过使用break和continue，但是它不起作用。

问题2：我发现我可以在循环...我们不能这样做，在C＃中...为什么PowerShell允许我们这样做？

解决方案

项目＃1。在 foreach 循环中放置 break 会退出循环，但不会停止管道。这听起来像你想要的东西是这样的：
$ b $ pre $ $ $ $ $ $ $ $ $ foreach $ $ $ $ todo）{
if（$ thing -eq'some_condition'）{
break
}
}


项目＃2。 PowerShell允许你修改一个数组内的 foreach 循环内的数组，但是这些变化直到退出循环才会生效。尝试运行下面的代码作为例子。

  $ a = 1,2,3 
 foreach（$ value in $ a）{
写主机$值
} 
写主机$ a 
  

我不能评论为什么PowerShell的作者允许这样做，但大多数其他脚本语言（ Perl ， Python 和shell）允许类似的结构。

I have the following code:

$project.PropertyGroup | Foreach {
    if($_.GetAttribute('Condition').Trim() -eq $propertyGroupConditionName.Trim()) {
        $a = $project.RemoveChild($_);
        Write-Host $_.GetAttribute('Condition')"has been removed.";
    }
};

Question #1: How do I exit from ForEach? I tried using "break" and "continue", but it doesn't work.

Question #2: I found that I can alter the list within a foreach loop... We can't do it like that in C#... Why does PowerShell allow us to do that?

解决方案

Item #1. Putting a break within the foreach loop does exit the loop, but it does not stop the pipeline. It sounds like you want something like this:

$todo=$project.PropertyGroup 
foreach ($thing in $todo){
    if ($thing -eq 'some_condition'){
        break
    }
}

Item #2. PowerShell lets you modify an array within a foreach loop over that array, but those changes do not take effect until you exit the loop. Try running the code below for an example.

$a=1,2,3
foreach ($value in $a){
  Write-Host $value
}
Write-Host $a

I can't comment on why the authors of PowerShell allowed this, but most other scripting languages (Perl, Python and shell) allow similar constructs.

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