PsfValidateSet

Synopsis

Describes how to use the [PsfValidateSet()] validation attribute.

Description

The [PsfValidateSet()] validation attribute can be used to validate input against a list of legal values. Its main use-case over [ValidateSet()] is the ability to dynamically calculate those values and to integrate into the PSFramework Tab Completion Feature.

Note: In scenarios where you have a static list of legal values, [ValidateSet()] is the clearly superior choice! [PsfValidateSet()] alone does not provide any tab completion and must be combined with the PSFramework Tab Completion Feature, in order to provide it.

Example

[CmdletBinding()]
param (
    [PsfValidateSet(ScriptBlock = { (Get-ChildItem "C:\Users\").Name  })]
    [string]
    $Path
)

Ensures that input matches the values returned by the scriptblock (which will be the names of all profile folders).

[CmdletBinding()]
param (
    [PsfValidateSet(TabCompletion = 'MyModule.UserProfiles')]
    [string]
    $Path
)

Uses the tab completion scriptblock registered under the name 'MyModule.UserProfiles' in order to validate the input. For more details, check out the PSFramework Tab Completion Feature.

Combining this validation attribute with the PSFramework Tab Completion Feature enables combining dynamic tab completion with dynamic input validation, without having to resort to dynamic parameters.

Properties

Name:       ScriptBlock
Positional: False
Named:      True

The scriptblock to generate the list of legal values the input will be compared with.

Name:       TabCompletion
Positional: False
Named:      True

The name of the tab completion scriptblock to also use for validation purposes. Using this does not confer the tab completion offered by the scriptblock - it must still be registered to command and parameter as defined in the PSFramework Tab Completion Feature.

Name:       Values
Positional: False
Named:      True

A static list of legal values to compare the input with. Included for completeness sake, but generally there should be no reason to use this over the plain old [ValidateSet()] attribute, if you already have a list of static values.

Name:       ErrorMessage
Positional: False
Named:      True

The message to write when the input does not equal any of the list of legal values. This text will be formatted using the default string formatter, inserting the original input into {0} and the legal values into {1} if present.

Generally there should be no reason to override the default message of “Cannot accept {0}, specify any of the following values: ‘{1}’”

Name:       ErrorString
Positional: False
Named:      True

The name of a localized string to use to write a localized error message when the input does not equal any of the legal values. This text will be formatted using the default string formatter, inserting the original input into {0} and the legal values into {1} if present.

The name needs to be module-qualified. For example "MyModule.Validation.UserProfiles" rather than just "Validation.UserProfiles" as would be the case on Write-PSFMessage.

Generally there should be no reason to override the default message of “Cannot accept {0}, specify any of the following values: ‘{1}’”, unless you need a localized version.

Notes

Back to Validation Attributes

Version	1.0
Written on:	2019-09-21
Updated on:	2019-09-21