英文:
Find out if variable is null or an array containing null variables in PowerShell
问题
我正在尝试确定一个变量是否为null 或 是否为包含null变量的数组。
因此，例如，一个简短的表达式，对于以下每一个都将匹配'false'，但对于其他任何情况都将匹配'true'：
$nullvariable = $null
$nullvariable1 = @($null)
$nullvariable2 = @($null, $null)
$nullvariable3 = @("1", $null)
上下文：我有一些Compare-Object调用，我试图避免'Cannot bind argument to parameter 'ReferenceObject' because it is null'错误。这里的第一个答案：https://stackoverflow.com/a/45634900/12872270 可以工作，但它的代码不够清晰易懂。
其他答案使用了一个'if'语句，这更易读，但在我的测试中，Compare-Object 不仅仅对 $null 失败，还对包含 null 条目的任何数组也失败 - 使用'if'的给定示例未考虑到这一点。
检测包含null变量的数组似乎是一个单独的问题，因此提出这个问题。
英文:
I am trying to find out if a variable is null or is an array containing null variables.
So for example, a short expression that will match 'false' for each of the following, but 'true' for anything else:
$nullvariable = $null
$nullvariable1 = @($null)
$nullvariable2 = @($null, $null)
$nullvariable3 = @("1", $null)
Context: I have some Compare-Object calls where I am trying to avoid 'Cannot bind argument to parameter 'ReferenceObject' because it is null' errors. The first answer here: https://stackoverflow.com/a/45634900/12872270 works but it's not very legible/comprehensible code.
The remaining answers use an 'if' statement which is more legible, but in my testing Compare-Object doesn't just fail for $null, but also any array containing null entries - the given examples using 'if' don't account for that.
Detecting an array containing null variables seems like a separate problem in its own right anyway, hence the question.
答案1
得分: 2
由于包含运算符可以针对标量和集合进行评估，因此在这种情况下，您可以使用-contains或-in与任何变量，结果将是$true：
$null -in $nullvariable # True
$nullvariable1 -contains $null # True
$null -in $nullvariable2 # True
$nullvariable3 -contains $null # True
英文:
Since containment operators can evaluate against scalars as well as collections, in this case you can either use -contains or -in with any of your variables and the result would be $true:
$null -in $nullvariable # True
$nullvariable1 -contains $null # True
$null -in $nullvariable2 # True
$nullvariable3 -contains $null # True
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