Switch parameters and powershell.exe -File parameter

Question

According Microsoft:

In rare cases, you might need to provide a Boolean value for a switch parameter. To provide a Boolean value for a switch parameter in the value of the File parameter, enclose the parameter name and value in curly braces, such as the following: -File .\\Get-Script.ps1 {-All:$False}

I have a simple script:

[CmdletBinding()] 
Param
(
    [switch] $testSwitch
)
$testSwitch.ToBool()

Next I am trying to run it this way:

powershell -file .\1.ps1 {-testSwitch:$false}

As result I receive an error:

But if believe Microsoft it should work.

If I delete [CmdletBinding] attribute this error will not occur, but for some reasons $testSwitch.ToBool() returns False despite whether I pass $True or $False .

Why? What are the reasons of this behaviour?

Answer 1

The workaround is to not use the -File parameter:

c:\scripts>powershell.exe .\test.ps1 -testswitch:$true
True
c:\scripts>powershell.exe .\test.ps1 -testswitch:$false
False

It is also an active bug on Microsoft Connect

Answer 2

There are ways to make this work, for instance expanding the string :

[CmdletBinding()]
Param(
  [Parameter()]$testSwitch
)

$ExecutionContext.InvokeCommand.ExpandString($testSwitch)

However, you don't really need to do that. Simply run the script with or without the switch and check for the presence of the switch parameter:

[CmdletBinding()]
Param(
  [switch][bool]$testSwitch
)

$testSwitch.IsPresent

Demonstration:

C:\>
True

C:\>
False