Question

我正在尝试生成一个输出字符串，例如Item1, Item2，并用逗号分隔符将其连接起来。为此，我们在Select-Object -Property中启动一个空数组。

检查此代码：

$Test =  @(
    [PSCustomObject]@{
        Name = 'Test'
    }
    [PSCustomObject]@{
        Name = 'Test2'
    }
) | Select-Object -Property @{N = 'Problem'; E = { @() } },
@{N = 'EmployeeType'; E = { $null } }, *

foreach ($R in $Test) {
    $R.Problem += 'Item1'
    $R.Problem += 'Item2'
}


$Test | Select-Object -Property @{Name = 'Problem'; Expression = { $_.Problem -join "; " } }, * -ExcludeProperty Problem | fl

结果：

Problem      : Item1Item2
Name         : Test

Problem      : Item1Item2
Name         : Test2

为什么属性Problem串联为String而不是Array？如何将其转换为Array？

Answer 1

要实例化计算所得属性的表达式中的空数组，Option Explicit 'Copy a range Sub CopyRange() Dim ws1 As Workbook, ws2 As Workbook 'It's better to declare sheets and avoid activate Set ws1 = Workbooks("Book1") Set ws2 = Workbooks("Book2") 'Copy from ws1(Book1), sheet "Test" & range A1:A5 to ws2 (Book2), sheet "sheet1" & range A1 ws1.Worksheets("Test").Range("A1:A5").Copy ws2.Worksheets("Sheet1").Range("A1").PasteSpecial Paste:=xlPasteValues End Sub是不够的，因为PowerShell会将其展平并且变为$ null。

改为使用@()

,@()

返回：

$Test =  @(
    [PSCustomObject]@{
        Name = 'Test'
    }
    [PSCustomObject]@{
        Name = 'Test2'
    }
) | Select-Object -Property @{N = 'Problem'; E = { ,@() } },
                            @{N = 'EmployeeType'; E = { $null } }, *

foreach ($R in $Test) {
    $R.Problem += 'Item1'
    $R.Problem += 'Item2'
}

$Test | Select-Object -Property @{Name = 'Problem'; Expression = { $_.Problem -join "; " } }, * -ExcludeProperty Problem | fl

Answer 2

不幸的是，这种创建空数组的方法行不通。

PS C:\users\js> $test[0].problem.gettype()
You cannot call a method on a null-valued expression.
At line:1 char:1
+ $test[0].problem.gettype()
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

PS C:\users\js> $test[0].problem -eq $null
True

顺便说一句，使用“ + =”杀死幼犬。

从选择对象启动数组

2 个答案: