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ValidateScript Attribute Declaration

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The ValidateScript attribute specifies a script that's used to validate a parameter or variable value. PowerShell pipes the value to the script, and generates an error if the script returns $false or if the script throws an exception.

When you use the ValidateScript attribute, the value that's being validated is mapped to the $_ variable. You can use the $_ variable to refer to the value in the script.

Syntax

[ValidateScriptAttribute(ScriptBlock scriptBlock)]
[ValidateScriptAttribute(ScriptBlock scriptBlock, Named Parameters)]

Parameters

  • scriptBlock - (System.Management.Automation.ScriptBlock) Required. The script block used to validate the input.
  • ErrorMessage - Optional named parameter - The item being validated and the validating scriptblock are passed as the first and second formatting arguments.

Note

The ErrorMessage argument was added in PowerShell 6.

Remarks

  • This attribute can be used only once per parameter.
  • If this attribute is applied to a collection, each element in the collection must match the pattern.
  • The ValidateScript attribute is defined by the System.Management.Automation.ValidateScriptAttribute class.

See Also

System.Management.Automation.ValidateScriptAttribute

Writing a Windows PowerShell Cmdlet