Parameter validation in PowerShell - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this PowerShell function call with parameter validation?

Consider the following PowerShell function that validates its parameter. What will be the output when calling Test-Param -Number 15?

PowerShell

function Test-Param {
  param(
    [ValidateRange(1,10)]
    [int]$Number
  )
  "Number is $Number"
}

Test-Param -Number 15

A No output, function silently ignores invalid input

B Number is 15

C ValidationException: Cannot validate argument on parameter 'Number'. The argument 15 is less than the minimum allowed range of 1.

D ValidationException: Cannot validate argument on parameter 'Number'. The argument 15 is greater than the maximum allowed range of 10.

💡 Hint

Think about what happens when a parameter value is outside the allowed range in PowerShell parameter validation.

The function uses [ValidateRange(1,10)] which restricts the parameter to values between 1 and 10. Passing 15 violates this, causing a ValidationException with a message about exceeding the maximum allowed range.

💻 Command Output

intermediate

What error does this PowerShell function produce when called with an invalid string?

Given this function with parameter validation, what error message appears when calling Check-Name -Name 'John123'?

PowerShell

function Check-Name {
  param(
    [ValidatePattern('^[a-zA-Z]+$')]
    [string]$Name
  )
  "Name is $Name"
}

Check-Name -Name 'John123'

A ValidationException: Cannot validate argument on parameter 'Name'. The argument 'John123' does not match the pattern '^[a-zA-Z]+$'.

B No output, function returns null

C RuntimeException: Invalid characters in parameter 'Name'.

D Name is John123

💡 Hint

Look at the regex pattern used in ValidatePattern and what input is given.

The pattern '^[a-zA-Z]+$' allows only letters. 'John123' contains digits, so it fails validation and throws a ValidationException with a message about the pattern mismatch.

📝 Syntax

advanced

Which option correctly uses ValidateSet to restrict parameter values?

You want to create a function parameter that only accepts the values 'Red', 'Green', or 'Blue'. Which of the following parameter declarations is correct?

PowerShell

function Set-Color {
  param(
    # Parameter declaration here
  )
  "Color set to $Color"
}

A

[ValidateSet('Red','Green','Blue')]
[int]$Color

B

[ValidateSet('Red','Green','Blue')]
[string]$Color

C

[ValidateSet('Red','Green','Blue')]
[bool]$Color

D

[ValidateSet('Red','Green','Blue')]
[array]$Color

💡 Hint

Think about the data type that matches color names.

ValidateSet restricts the parameter to specific string values. The parameter type must be string to accept color names. Using int, bool, or array types will cause errors or unexpected behavior.

🚀 Application

advanced

What is the output of this function when called with -Age 25?

This function uses multiple parameter validations. What will it output when called as Check-Age -Age 25?

PowerShell

function Check-Age {
  param(
    [ValidateRange(18,30)]
    [ValidateNotNull()]
    [int]$Age
  )
  if ($Age -ge 21) {
    "Adult"
  } else {
    "Young Adult"
  }
}

Check-Age -Age 25

A Adult

B Young Adult

C ValidationException: Age is out of range

D No output

💡 Hint

Check the range and the if condition inside the function.

The parameter Age is validated to be between 18 and 30 and not null. 25 passes validation. Since 25 is greater or equal to 21, the function outputs 'Adult'.

🧠 Conceptual

expert

Which parameter validation attribute prevents null or empty strings?

You want to ensure a string parameter is not null or empty in your PowerShell function. Which validation attribute should you use?

A [ValidateNotNull()]

B [ValidateNotEmpty()]

C [ValidateNotNullOrEmpty()]

D [ValidateString()]

💡 Hint

One attribute specifically checks for both null and empty strings.

[ValidateNotNull()] only prevents null values but allows empty strings. [ValidateNotNullOrEmpty()] prevents both null and empty strings. The other options are not valid PowerShell validation attributes.