选择不存在的属性时没有错误 [英] No error when selecting non-existing property

问题描述

我希望 PowerShell 在尝试选择不存在的属性时抛出错误，但我得到的是空列作为输出.示例:

I want PowerShell to throw an error when trying to select non-existing properties, but instead I get empty column as output. Example:

$ErrorActionPreference=[System.Management.Automation.ActionPreference]::Stop;
Set-StrictMode -Version 'Latest'
Get-Process *ex* | Select-Object Id,ProcessName,xxx

   Id ProcessName   xxx
   -- -----------   ---
 9084 explorer
11404 procexp

我编写了一个脚本，该脚本通过 Import-Csv 导入多个文本文件，但这些文件中的标题可能会发生变化，最终我会将空列加载到系统中.

I wrote a script that is importing multiple text files by Import-Csv, but headers in those file may change, and I'll end up with empty columns being loaded to the system.

这是我检查标题是否匹配的方式:

This is how I'm checking if the headers match:

$csv = Import-Csv -Delimiter ';' -Path $file.FullName 
$FileHeaders = @(($csv | Get-Member -MemberType NoteProperty).Name) 
if (Compare-Object $ProperHeaders $FileHeaders) {'err'} else {'ok'}

我知道这就是 PowerShell 的工作方式，但正如@Matt 提到的那样，Set-StrictMode 文档确实对我有点误导.我只是希望 Select-Object 有某种-NoNewImplicitProps"或-ReadOnlyPipeline"开关可以为我完成这项工作:).感谢您的回答.

I know that's the way PowerShell works, but Set-StrictMode documentation was indeed a little misleading for me, as @Matt mentioned. I just wish Select-Object had some kind of "-NoNewImplicitProps" or "-ReadOnlyPipeline" switch that would do the job for me :). Thanks for the answers.

推荐答案

您实际上使用的是什么 有些人会称之为功能.这是使用 Add-Member 对所有数组成员添加一个空列.

You are actually using what some people would call a feature. That is a simpler rendition of using Add-Member on all the array members to add an empty column.

在 Import-CSV 的情况下，您在这种情况下所做的是检查 之前的属性名称选择你在哪里打电话.

In the case of Import-CSV what you do in that case is check the property names before the Select where you call them.

$data = Import-csv C:\Temp\file.csv 
$props = $data | Get-member -MemberType 'NoteProperty'  | Select-Object -ExpandProperty Name

我可以看到文档在说 时有点误导Set-StrictMode:

I can see the documentation be a little misleading when it says for Set-StrictMode:

禁止引用对象不存在的属性.

Prohibits references to non-existent properties of an object.

但在这种情况下，您不是尝试获取属性引用，而是使用 Select-Object cmdlet 的函数.尽管以下内容会产生错误

But in this case you are not trying to get the property reference but using a function of the Select-Object cmdlet. The following would have generated an error though

PS C:\Users\mcameron> Set-StrictMode -Version 'Latest'
(Get-Process *ex*).Bagels

The property 'Bagels' cannot be found on this object. Verify that the property exists.
At line:2 char:1
+ (Get-Process *ex*).Bagels
+ ~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], PropertyNotFoundException
    + FullyQualifiedErrorId : PropertyNotFoundStrict

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