它是正確的錯誤嗎（看起來throw不起作用）？

我有一個簡單的腳本：

$ErrorPreference = 'Stop'
$user = [System.Security.Principal.WindowsIdentity]::GetCurrent().Name
if ($null -eq $user) {
    throw 'User and password are required'
} else {
    $password = (Get-Credential -credential $user).Password
    if ($null -eq $password) {
        throw 'Password is required'
    } else {
        $plainpassword = [System.Net.NetworkCredential]::new("", $password).Password
        $service = Get-WMIObject -class Win32_Service -filter "name='myservice'"
        if ($null -ne $service) {
            [void]$service.change($null, $null, $null, $null, $null, $false, $user, $plainpassword)
        } else {
            throw 'Service was not installed properly'
        }
    }
}

當我在憑據輸入對話框中按“取消”時，用戶和密碼必須是$null. 所以，我在$null. 但我收到一個錯誤：

Get-Credential : Cannot bind argument to parameter 'Credential' because it is null.
At C:....ps1:6 char:45
      $password = (Get-Credential -credential $user).Password
                                              ~~~~~
      CategoryInfo          : InvalidData: (:) [Get-Credential], ParameterBindingValidationException
      FullyQualifiedErrorId : ParameterArgumentValidationErrorNullNotAllowed,Microsoft.PowerShell.Commands.GetCredenti
   alCommand

Password is required
At C:....ps1:8 char:9
          throw 'Password is required'
          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      CategoryInfo          : OperationStopped: (Password is required:String) [], RuntimeException
      FullyQualifiedErrorId : Password is required

我看到throw 'Password is required'但同時我看到：

Get-Credential : Cannot bind argument to parameter 'Credential' because it is null.

我希望如果$user是，$null那么它不應該發生，我什至會在這條線之前退出。為什么會發生這種情況以及如何處理？

PS。這似乎$ErrorPreference = 'Stop'是多余的，只是為了確定......

uj5u.com熱心網友回復：

tl;博士

# Get the current user's domain-qualified name, using whoami.exe for simplicity
# (same as [System.Security.Principal.WindowsIdentity]::GetCurrent().Name).
# (Alternatively, use "$env:USERDOMAIN\$env:USERNAME", or
#  if the domain prefix isn't needed just $env:USERNAME)
$user = whoami

# Prompt for the current user's password.
# Note the use of -UserName rather than -Credential.
# -Message is then unfortunately *required* in *Windows PowerShell*,
# but no longer in *PowerShell (Core) 7 *
$cred = get-credential -UserName $user -Message 'Enter your credentials:'

# Abort, if the prompt was canceled (return value is $null)
# or an empty password was given (a [pscredential] instance was returned,
# but the length of its .Password property is 0).
if ($null -eq $cred -or $cred.Password.Length -eq 0) { throw "Password is required." }

# Get the plain-text password for the later WMI method call.
# !! THIS SHOULD GENERALLY BE AVOIDED.
$password = $cred.GetNetworkCredential().Password

# ... Make your WMI call

至于你嘗試了什么：

Get-Credential -credential $user

Get-Credential的-Credential引數是一個奇怪的野獸，最好避免，因為它期望一個已經是實體[pscredential]的引數作為它的引數。

正如您所做的那樣，僅將用戶名傳遞給它，以便預先填寫用戶名欄位，原則上是可行的，但是當您取消對話框時會導致（陳述句終止）錯誤，并伴隨著令人困惑的錯誤訊息：

• Cannot bind argument to parameter 'Credential' because it is null- 盡管您顯然確實將引數傳遞給-Credential.

• 錯誤的原因是，由于引數被屬性修飾，因此將僅使用名稱傳遞給-Credential 自身會觸發憑據提示，并且這發生在從該提示接收回傳值之前：-CredentialSystem.Management.Automation.CredentialAttribute Get-Credential

• 如果該提示被取消，則回傳，然后$null嘗試系結到引數會觸發錯誤。$null-Credential

• 相反，如果您傳遞一個預先存在的[pscredential]實體，則不會顯示任何提示，并且該實體只是通過 傳遞。

改用-UserName引數（假設你需要在提示中預填一個用戶名），這樣行為更明智；不幸的是，出于語法原因，在Windows PowerShell中，您還必須使用引數，-Message如上所示；幸運的是，這不再是PowerShell (Core) 7 的要求：

• 如果取消對話框，$null則回傳^[1]，不會發生錯誤。

  • 注意：在PowerShell (Core) 7 中，Get-Credential不再使用GUI對話框提示，而是直接在控制臺視窗中提示。您不能再取消這樣的提示，但是您可以按Ctrl C，這會自動終止整個腳本。

• 否則，將[pscredential]回傳一個實體，其中包含用戶名和密碼作為[securestring].

^{[1] 從技術上講，沒有輸出，PowerShell 使用有時稱為“AutomationNull”的特殊單例發出信號 - 請參閱此答案。但是，在比較等運算式-eq中，它的行為類似于$null.}

uj5u.com熱心網友回復：

因為該 cmdlet 需要引數，所以您必須將呼叫包裝在 try catch 塊中以捕獲該 ParameterBindingException

$ErrorPreference = 'Stop'
$user = [System.Security.Principal.WindowsIdentity]::GetCurrent().Name
if ($null -eq $user) {
    throw 'User and password are required'
} else {
    try {
        $cred = Get-Credential -Credential $user
        $password = ($cred.getNetworkCredential()).Password   
        $service = Get-WMIObject -class Win32_Service -filter "name='myservice'"
        if ($null -ne $service) {
            [void]$service.change($null, $null, $null, $null, $null, $false, $user, $password)
        } else {
            throw 'Service was not installed properly'
        }
    }
    catch [System.Management.Automation.ParameterBindingException]{
        throw 'Password is required'
    }
}

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