Use ValidateSet Command in param block to define parameter

Question

I need to write a function which defines a bool Parameter automatically with [ValidateScript()].

function Deploy-App {
    Param(
        [Parameter(Position=0)]
        [ValidateScript({if (Test-Path .\DeployFiles.txt) { $UseFilepathFile = $true }})]
        [Alias("u")]
        [bool]$UseFilepathFile
    )

    Get-Location
    Write-Host $UseFilepathFile
}

Why does this always return $false even though the file exists in the current location? Is the usage of ValidateScript() wrong and I can't use it like this? How else would I tackle my problem?

Your code doesn't make sense. ValidateScript() is for validating values passed into a function, not for assigning values to variables. The latter would go into the function bod, e.g. $UseFilepathFile = Test-Path .\DeployFiles.txt. Please take a step back and describe the actual problem you're trying to solve. What do you need this for? — Ansgar Wiechers
– Ansgar Wiechers, Commented Dec 10, 2016 at 16:52

4c74356b41 · Accepted Answer · 2016-12-10 16:51:29Z

2

You are using ValidateScript the wrong way, ValidateScript is used to validate the input, not set it. Also, you must return $true from the ValidateScript, else the script won't work.

What you need is to check if that file exists inside the body of the script itself.

if (Test-Path .\DeployFiles.txt) { $UseFilepathFile = $true }

answered Dec 10, 2016 at 16:51

4c74356b41

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