The [CmdletBinding] attribute helps determine how parameters are bound to a given function or ScriptBlock.
It’s also the formal dividing line between an advanced function and a simple function.
We can put a [CmdletBinding] can be put above the param() block in any ScriptBlock.
{
[CmdletBinding()]
param()
}
CmdletBinding is a very useful thing to understand.
Let’s take a look at a few common things you can do with it.
Parameter Sets cam be powerful. They allow your parameters to handle several different sets of input.
Unfortunately, parameter sets can also cause some confusion in parameter binding.
Setting a DefaultParameterSetName may help clear up that confusion.
function WinLoseOrDraw
{
[CmdletBinding(DefaultParameterSetName='Draw')]
param(
[Parameter(ParameterSetName='Win')]
[switch]
$Win,
[Parameter(ParameterSetName='Lose')]
[switch]
$Lose,
[Parameter(ParameterSetName='Draw')]
[switch]
$Draw
)
$psCmdlet.ParameterSetName
}
WinLoseOrDraw
PowerShell can Prompt for Confirmation. To support this, we use the SupportsShouldProcess property on [CmdletBinding]
function shouldI {
[CmdletBinding(SupportsShouldProcess,ConfirmImpact='High')]
param($DoThis)
if ($psCmdlet.ShouldProcess($DoThis)) {
"You should do this $doThis"
} else {
"You should not do this $doThis"
}
}
shouldI -DoThis "On a boat"
shouldI -DoThis "In a moat"
By default, parameters have a position that reflects the order they’re declared.
You can turn this behavior off by using PositionalBinding=$false in [CmdletBinding].
This is especially useful when combined with a parameter attribute that uses ValueFromRemainingArguments
function FreeFormFunction {
[CmdletBinding(PositionalBinding=$false)]
param(
$NamedParameter,
[Parameter(ValueFromRemainingArguments)]
$RestOfParameters,
[Parameter(Position=0)]
$FirstParameter
)
$psBoundParameters
}
FreeFormFunction a b c d
FreeFormFunction a b c -NamedParameter d