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Please try this:
function f1 { param( [Parameter(Mandatory=$true,ValueFromPipelineByPropertyName=$true)] [string] $Text ) $text } function f2 { param( [Parameter(Mandatory=$true,ValueFromPipelineByPropertyName=$true)] #[string] $Text ) $text } function f3 { param( [Parameter(Mandatory=$False,ValueFromPipelineByPropertyName=$true)] [string] $Text ) $text } f1 '' f2 '' f3 '' Here f1 throws an error. Now try
f2 $null f3 $null This time only f2 throws an error. What I want is a function f, so that
f '' # is accepted f $null # returns an error 
985
You can pass the parameters in the PowerShell function and to catch those parameters, you need to use the arguments. Generally, when you use variables outside the function, you really don't need to pass the argument because the variable is itself a Public and can be accessible inside the function.
To validate the file or folder path inside the PowerShell function parameter, we need to use the ValidateScript command.
To make a parameter mandatory add a "Mandatory=$true" to the parameter description. To make a parameter optional just leave the "Mandatory" statement out. Make sure the "param" statement is the first one (except for comments and blank lines) in either the script or the function.
The Mandatory attribute blocks null and empty values and prompts you for a value. To allow empty values (including null) add the AllowEmptyString parameter attribute:
function f1 { param( [Parameter(Mandatory=$true,ValueFromPipelineByPropertyName=$true)] [AllowEmptyString()] [string]$Text ) $text } If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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