Powershell 在字符串中使用null

我发现，对于PowerShell中的字符串，使用

$null

是不可能的。虽然我已经使用了以下解决方法，但我想知道是否有更好的方法

基本上我需要3种状态的字符串

$null

，

'

（空），

'some string'

• 第一个意思是——不要执行
• 第二个一-明文
• 用新值替换文本

下面是我选择开关

-ClearText

的变通代码。请记住，如果字段是

$null

，我就不能添加

Set WordTextText

，但因为我是在嵌套场景中这样做的，所以我更喜欢按

$null

的方式来做

function Remove-WordText {
    Param(
        [parameter(ValueFromPipelineByPropertyName, ValueFromPipeline)][Xceed.Words.NET.InsertBeforeOrAfter] $Paragraph,
        [int] $Index = 0,
        [int] $Count = $($Paragraph.Text.Length),
        [bool] $TrackChanges,
        [bool] $RemoveEmptyParagraph,
        [bool] $Supress = $false
    )
    if ($Paragraph -ne $null) {
        Write-Verbose "Remove-WordText - Current text $($Paragraph.Text) "
        Write-Verbose "Remove-WordText - Removing from $Index to $Count - Paragraph Text Count: $($Paragraph.Text.Length)"
        $Paragraph.RemoveText($Index, $Count, $TrackChanges, $RemoveEmptyParagraph)
    }
    if ($Supress) { return } else { return $Paragraph }
}

function Set-WordTextText {
    param(
        [parameter(ValueFromPipelineByPropertyName, ValueFromPipeline)][Xceed.Words.NET.InsertBeforeOrAfter] $Paragraph,
        [alias ("S")] [AllowNull()][string] $Text,
        [switch] $ClearText,
        [bool] $Supress = $false
    )
    if ($Paragraph -ne $null) {
        if (-not [string]::IsNullOrEmpty($Text)) {
            if ($ClearText -eq $true) {
                Write-Verbose 'Set-WordTextText - Clearing Text $ClearText is True'
                $Paragraph = Remove-WordText -Paragraph $Paragraph
            }
            Write-Verbose "Set-WordTextText - Appending Value $Text"
            $Paragraph = $Paragraph.Append($Text)
        }
    }
    if ($Supress) { return } else { return $Paragraph }
}

我基本上在函数中执行它：

$Paragraph[$i] = $Paragraph[$i] | Set-WordTextText -Text $Text[$i] -ClearText:$ClearText -Supress $false
$Paragraph[$i] = $Paragraph[$i] | Set-WordTextColor -Color $Color[$i] -Supress $false
$Paragraph[$i] = $Paragraph[$i] | Set-WordTextFontSize -FontSize $FontSize[$i] -Supress $false
$Paragraph[$i] = $Paragraph[$i] | Set-WordTextFontFamily -FontFamily $FontFamily[$i] -Supress $false
$Paragraph[$i] = $Paragraph[$i] | Set-WordTextBold -Bold $Bold[$i] -Supress $false
$Paragraph[$i] = $Paragraph[$i] | Set-WordTextItalic -Italic $Italic[$i] -Supress $false

---

它仅在值不为null时执行操作。因此，“包装器”函数可以有1到20个参数，并且仅在给定参数时执行

如果$paragration处于三种状态之一，则根据您正在执行的功能决定要执行的操作。像这样的东西可能会有帮助

if ($null -eq $Paragraph) { 
    Write-Host "Paragraph is Null, do not execute"
    return
}
elseif ([string]::IsNullOrEmpty($Paragraph.Text)) { 
    # this depends on the function you are in.
    # if inside Remove-WordText() you don't have to do anything because it is already empty
    # you can check the function currently executed with $MyInvocation.MyCommand.Name
    if ($MyInvocation.MyCommand.Name -eq 'Remove-WordText') {
        Write-Host "Paragraph.Text is Null or Empty, clear text"
        $Paragraph.RemoveText($Index, $Count, $TrackChanges, $RemoveEmptyParagraph)
    else {
        # however, if you're inside Set-WordTextText() you need to decide if $Text
        # is not empty aswell and if not, you append the Text tp $Paragraph
        if (-not [string]::IsNullOrEmpty($Text)) {
            Write-Verbose "Set-WordTextText - Appending Value $Text"
            $Paragraph = $Paragraph.Append($Text)
        }
    }
}
else {
    Write-Host "Paragraph.Text has value, appending text"
    $Paragraph = $Paragraph.Append($Text)
}

---

如果为参数指定类型

[String]

，希望这对您有所帮助，因为该参数将成为类型化变量，并且不能再为

$null

。即使将

$null

传递给参数，该值也将自动转换为空字符串。要允许参数为

$null

或字符串（空或非空），您需要如下内容：

function Set-WordTextText {
    Param(
        ...
        [Parameter(Mandatory=$false)]
        [AllowNull()]
        $Text = $null,
        ...
    )

    if ($_ -ne $null -and $_ -isnot [String]) {
        throw 'Invalid argument for parameter -Text.'
    }

    ...
}

---

我不明白你的逻辑$段落为空是一种选择，效果很好。它是一个单独的值$Text，它是一个字符串，不能为null，我需要它为null以停止执行。否则我需要提供额外的参数。若我能够使用$null，我可以简单地跳过为函数提供参数，它就不会执行了。就像现在一样，若我不定义参数，我会跳过使用-Clear，它实际上会擦除值，而不是跳过它。这很有意义。出于某种原因，我太专注于将其键入为[string]，以至于我不接受任何类型。谢谢