Add Section on Variable Validation outside of Parameters.

[gerane]

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In PowerShell v3, the ability to use Validation attributes on variables outside of parameters was added.

It is mentioned here in the New v3 Language Features Page.

Here are a few quick examples.

ValidateRange

PS> [ValidateRange(1,10)][int]$ValidateRange = 1
PS> $ValidateRange = 3
PS> $ValidateRange = 11 
The variable cannot be validated because the value 11 is not a valid value for the x variable. 
At line:1 char:1 
+ $ValidateRange = 11 
+ ~~~~~~~ 
    + CategoryInfo          : MetadataError: (:) [], ValidationMetadataException 
    + FullyQualifiedErrorId : ValidateSetFailure

ValidateSet

PS> [ValidateSet('Test1','Test2','Test3')][string]$ValidateSet = 'Test1'
PS> $ValidateSet = 'Test2'
PS> $ValidateSet = 'Test4'
The variable cannot be validated because the value Test4 is not a valid value for the x variable.
At line:1 char:1
+ $ValidateSet = 'Test4'
+ ~~~~~~~~~~~~
    + CategoryInfo          : MetadataError: (:) [], ValidationMetadataException
    + FullyQualifiedErrorId : ValidateSetFailure

ValidateNotNullOrEmpty

PS> [ValidateNotNullOrEmpty()][string]$ValidateNotNullOrEmpty = 'Test1'
PS> $ValidateNotNullOrEmpty = 'Test'
PS> $ValidateNotNullOrEmpty = ''
The variable cannot be validated because the value  is not a valid value for the x variable.
At line:1 char:1
+ $ValidateNotNullOrEmpty = ''
+ ~~~~~~~
    + CategoryInfo          : MetadataError: (:) [], ValidationMetadataException
    + FullyQualifiedErrorId : ValidateSetFailure

ValidateCount

PS> [ValidateCount(1,10)][array]$ValidateCount = @(1..9)
PS> $ValidateCount += 'test'
PS> $ValidateCount += 'test2'
The variable cannot be validated because the value System.Object[] is not a valid value for the ValidateCount variable.
At line:1 char:1
+ $ValidateCount += 'test2'
+ ~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : MetadataError: (:) [], ValidationMetadataException
    + FullyQualifiedErrorId : ValidateSetFailure

ValidateLength

PS> [ValidateCount(1,10)][string]$ValidateLength = 'Test1'
PS> $ValidateLength = 'Testing2'
PS> $ValidateLength = 'TestOverTen'
The variable cannot be validated because the value TestOverTen is not a valid value for the ValidateLength variable.
At line:1 char:1
+ $ValidateLength = 'TestOverTen'
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : MetadataError: (:) [], ValidationMetadataException
    + FullyQualifiedErrorId : ValidateSetFailure

ValidatePattern

PS> [ValidatePattern('^\d{3}[-.]?\d{3}[-.]?\d{4}$')][string]$ValidatePattern = '800-123-4567'
PS> $ValidatePattern = '000-000-0000
PS> $ValidatePattern = '000-000-00000'
The variable cannot be validated because the value 000-000-00000 is not a valid value for the ValidatePattern variable.
At line:1 char:1
+ $ValidatePattern = '000-000-00000'
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : MetadataError: (:) [], ValidationMetadataException
    + FullyQualifiedErrorId : ValidateSetFailure

ValidateScript

PS> [ValidateScript({Test-Path $_})][string]$ValidateScript = 'C:\Windows\System32\cmd.exe'
PS> $ValidateScript = 'C:\Windows\System32\powercfg.exe'
PS> $ValidateScript = 'C:\Windows\System32\DoesNotExist.exe'
The variable cannot be validated because the value C:\Windows\System32\DoesNotExist.exe is not a valid value for the ValidateScript variable.
At line:1 char:1
+ $ValidateScript = 'C:\Windows\System32\DoesNotExist.exe'
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : MetadataError: (:) [], ValidationMetadataException
    + FullyQualifiedErrorId : ValidateSetFailure