Parameter attributes (Mandatory, ValidateSet) in PowerShell - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of a script with Mandatory and ValidateSet attributes

What will be the output when running this PowerShell script without any parameters?

PowerShell

function Test-Param {
  param(
    [Parameter(Mandatory=$true)]
    [ValidateSet('Red','Green','Blue')]
    [string]$Color
  )
  "Selected color is $Color"
}

Test-Param

A Selected color is Green

B Error: The value provided is not in the ValidateSet.

C You must provide a value for the mandatory parameter 'Color'.

D Selected color is Red

💡 Hint

Think about what happens when a mandatory parameter is not provided.

The parameter 'Color' is mandatory, so running the function without providing it causes PowerShell to prompt for it or throw an error if running non-interactively.

💻 Command Output

intermediate

Output when passing invalid value to ValidateSet parameter

What happens when you run this script with the parameter value 'Yellow'?

PowerShell

function Test-Param {
  param(
    [Parameter(Mandatory=$true)]
    [ValidateSet('Red','Green','Blue')]
    [string]$Color
  )
  "Selected color is $Color"
}

Test-Param -Color Yellow

A Selected color is Yellow

B Error: Cannot validate argument on parameter 'Color'. The argument 'Yellow' does not belong to the set 'Red,Green,Blue'.

C Selected color is Red

D No output, script runs silently

💡 Hint

Check what ValidateSet does when an invalid value is passed.

ValidateSet restricts the parameter to specific values. Passing 'Yellow' causes a validation error.

📝 Syntax

advanced

Identify the correct syntax for Mandatory and ValidateSet attributes

Which option correctly declares a parameter named 'Mode' that is mandatory and accepts only 'Auto', 'Manual', or 'Off'?

A [Parameter(Mandatory=$true)][ValidateSet('Auto','Manual','Off')][string]$Mode

B [ValidateSet('Auto','Manual','Off')][Parameter(Mandatory=$true)][string]$Mode

C edoM$]gnirts[])'ffO','launaM','otuA'(teSetadilaV[])eurt$=yrotadnaM(retemaraP[

D [Parameter(Mandatory=$false)][ValidateSet('Auto','Manual','Off')][string]$Mode

💡 Hint

Mandatory attribute requires explicit assignment to $true or $false.

The correct syntax uses Mandatory=$true explicitly. Option A and C omit the assignment, causing syntax errors. Option A sets Mandatory to false, which is incorrect.

🚀 Application

advanced

Determine the output of a script using Mandatory and ValidateSet with default value

What will be the output of this script when run without parameters?

PowerShell

function Test-Param {
  param(
    [Parameter(Mandatory=$true)]
    [ValidateSet('Small','Medium','Large')]
    [string]$Size = 'Medium'
  )
  "Selected size is $Size"
}

Test-Param

A Selected size is Medium

B Error: Default value not allowed with Mandatory parameter.

C Selected size is Small

D You must provide a value for the mandatory parameter 'Size'.

💡 Hint

Consider how Mandatory and default values interact.

A parameter cannot have both Mandatory=$true and a default value. PowerShell will still require the parameter to be provided.

🧠 Conceptual

expert

Understanding behavior of Mandatory and ValidateSet in pipeline input

Given this function, what will be the output when piping the string 'Green' to it?

PowerShell

function Test-Param {
  param(
    [Parameter(Mandatory=$true, ValueFromPipeline=$true)]
    [ValidateSet('Red','Green','Blue')]
    [string]$Color
  )
  process {
    "Selected color is $Color"
  }
}

'Green' | Test-Param

A Selected color is Green

B You must provide a value for the mandatory parameter 'Color'.

C Error: Cannot validate argument on parameter 'Color'. The argument 'Green' does not belong to the set.

D No output

💡 Hint

Think about how pipeline input works with ValidateSet and Mandatory.

The string 'Green' is passed through the pipeline and matches the ValidateSet, so the function outputs the selected color.