使用開始，過程，結束在腳本塊

Question

是否有可能使用adavanced函數的特徵是在腳本塊Begin, Process, End？

例如我有以下腳本塊：

$startStopService = { 
Param(
    [bool] $startService)  

    if ($startService){ 
    ... 
    Start-Service "My-Service" 
    } 
    else { 
    Stop-Service "My-Service" 
    } 
} 

因爲我希望能夠控制腳本塊的詳細輸出我想塊更改爲：

$startStopService = { 
Param(
    [bool] $startService)  

    Begin { 
    $oldPreference = $VerbosePreference 
    $VerbosePreference = $Using:VerbosePreference 
    } 
    Process { 
    if ($startService){ 
     ... 
     Start-Service "My-Service" 
    } 
    else { 
     Stop-Service "My-Service" 
    } 
    } 
    End { 
    # Restore the old preference 
    $VerbosePreference = $oldPreference 
    } 
} 

這裏有沒有可能使用Begin, Process, End，儘管scriptblock不是一個cmdlet？我只是希望VerbosePreference恢復到舊值，無論是否發生錯誤。當然，我可以使用try{}finally{}作爲替代，但我發現Begin, Process, End更直觀。

THX

Answer 1

這是可能的，如在about_script_blocks描述：

一樣的功能，腳本塊可以包括DynamicParam，開始， 過程和結束關鍵字。欲瞭解更多信息，請參閱about_Functions 和about_Functions_Advanced。

---

爲了驗證這一點，我修改你的腳本塊，並運行此：

$startStopService = { 
Param(
    # a bool needs $true or $false passed AFAIK 
    # A switch is $true if specified, $false if not included 
    [switch] $startService 
)  

    Begin { 
    $oldPreference = $VerbosePreference 
    Write-Output "Setting VerbosePreference to Continue" 

    # $Using:VerbosePreference gave me an error 
    $VerbosePreference = "Continue" 
    } 
    Process { 
    if ($startService){ 
     Write-Verbose "Service was started" 
    } 
    else { 
     Write-Verbose "Service was not started" 
    } 
    } 
    End { 
    # Restore the old preference 
    Write-Output "Setting VerbosePreference back to $oldPreference" 
    $VerbosePreference = $oldPreference 
    } 

} 

Write-Verbose "This message will not print if VerbosePreference is the default SilentlyContinue" 

. $startStopService -startService 

Write-Verbose "This message will not print if VerbosePreference is the default SilentlyContinue" 

---

後，哪些功能是你嗎？如果運行一個腳本塊，但在腳本的其餘部分沒有改變$VerbosePreference時，你會打印詳細消息，請考慮使用[CmdletBinding()]和-Verbose標誌：

$startStopService = { 
    [CmdLetBinding()] 
    Param(
     [switch] $startService 
    ) 

    Write-Verbose "This is a verbose message" 

} 
Write-Verbose "This message will not print if VerbosePreference is the default SilentlyContinue" 

. $startStopService -verbose 

Write-Verbose "This message will not print if VerbosePreference is the default SilentlyContinue" 

---

編輯 - 調用命令

您的評論後，我尋找到的Invoke-Command功能。並發現很多不起作用的東西。

短的版本，我認爲這是最適合您：你可以宣佈一個腳本塊內$VerbosePreference = "Continue"，這將限制在腳本塊的範圍。之後無需改變。

$startStopService = { 
    [CmdLetBinding()] 
    Param(
     [parameter(Position=0)] 
     [switch]$startStopService, 

     [parameter(Position=1)] 
     [switch]$Verbose 
    ) 

    if($Verbose){ 
     $VerbosePreference = "Continue" 
    } 

    Write-Verbose "This is a verbose message" 

} 

Write-output "VerbosePreference: $VerbosePreference" 
Write-Verbose "This message will not print if VerbosePreference is the default SilentlyContinue" 

Invoke-Command -Scriptblock $startStopService -ArgumentList ($true,$true) 

Write-output "VerbosePreference: $VerbosePreference" 
Write-Verbose "This message will not print if VerbosePreference is the default SilentlyContinue" 

試圖通過-Verbose開關CommonParameter到Invoke-Command是一個沒有去。這使用標準Verbose開關參數，允許你傳遞$true/$false（或省略）來控制詳細的輸出。

_{相關：
about_Functions
about_Functions_Advanced}