Variables and function parameters can be automatically validated through validation attributes. Here is a simple example making sure $test1 can only store values between 1 and 10:
[ValidateRange(1,10)]$test1 = 10
Once you assign a value less than 1 or greater than 10 to it, PowerShell throws an exception. You just don’t have any control over the exception text.
By using a script validator, you can pick the error message yourself:
[ValidateScript({ If ($_ -gt 10) { throw 'You have submitted a value greater than 10. That will not work, dummy!' } Elseif ($_ -lt 1) { throw 'You have submitted a value lower than 1. That will not work, dummy!' } $true })]$test2 = 10
And here is the output:
PS C:\> $test2 = 4 PS C:\> $test2 = 11 You have submitted a value greater than 10. That will not work, dummy! At line:5 char:3 + { throw 'You have submitted a value greater than 10. That will not work, dummy ... + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : OperationStopped: (You have submitted a...not work, dummy!:String ) [], RuntimeException + FullyQualifiedErrorId : You have submitted a value greater than 10. That will not work, dummy! PS C:\> $test2 = -2 You have submitted a value lower than 1. That will not work, dummy! At line:7 char:3 + { throw 'You have submitted a value lower than 1. That will not work, dummy ... + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : OperationStopped: (You have submitted a...not work, dummy!:String ) [], RuntimeException + FullyQualifiedErrorId : You have submitted a value lower than 1. That will not work, dummy!
