Question

我目前正在撰写一份简单的PowerShell(5)书。它应当吸收用户的意见,然后根据投入执行一些任务。我将Validate写到投入参数,以验证用户的投入。根据PowerShell文件,验证是在编码操作之前进行的,因此,我改变了用户投入的价值。然而,这造成了错误。

考虑下面的简单例子。


  [CmdletBinding()]
    param (
        [Parameter(Mandatory=$true)]
        [ValidateScript({ $_ -gt 0 })]
        [int]$InputParameter
    )

    process {
       
        $InputParameter = -1

      
    }
}

Running TEST-FUNCTION 0 Yields an error

TEST-FUNCTION : Cannot validate argument on parameter  InputParameter . The " $_ -gt 0 " validation script for the
argument with value "0" did not return a result of True. Determine why the validation script failed, and then try the
command again.
At line:1 char:15
+ TEST-FUNCTION 0
+               ~
    + CategoryInfo          : InvalidData: (:) [TEST-FUNCTION], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationError,TEST-FUNCTION

这具有意义,因为它没有通过最初的确认。

However, running TEST-FUNCTION 1 also yields an error.

The variable cannot be validated because the value -1 is not a valid value for the InputParameter variable.
At line:12 char:9
+         $InputParameter = -1
+         ~~~~~~~~~~~~~~~~~
    + CategoryInfo          : MetadataError: (:) [], ValidationMetadataException
    + FullyQualifiedErrorId : ValidateSetFailure

The two function calls give two different errors. I’m not sure why I can’t change the value of the parameter after it has passed validation. Is there any workaround that can prevent the second round of evaluation? Thanks!

Answer 1

由于属性已附在https://learn.microsoft.com/en-us/dotnet/api/system. management.automation.psvariable?view=powershellsdk-7.4.0” rel=“nofollow noreferer”>PSVariable 元数据,简单的例子不需要:

[ValidateScript({ $_ -gt 0 })]
[int] $InputParameter = 1

(Get-Variable InputParameter).Attributes |
    Where-Object TypeId -EQ ([System.Management.Automation.ValidateScriptAttribute])

# ErrorMessage ScriptBlock TypeId
# ------------ ----------- ------
#               $_ -gt 0   System.Management.Automation.ValidateScriptAttribute

自<代码>。《<>ttributes/code>是一种收集,但你可以将其删除,但事实上,在你的职责中,更便于使用不同的名称:

$attributeToRemove = (Get-Variable InputParameter).Attributes |
    Where-Object TypeId -EQ ([System.Management.Automation.ValidateScriptAttribute])

$InputParameter = -1
# MetadataError: The variable cannot be validated because the value -1 is not a valid....

$null = (Get-Variable InputParameter).Attributes.Remove($attributeToRemove)

$InputParameter = -1 # OK

友情链接