PowerShell parameter sets allow you to control which parameters can be used together. If a parameter isn’t in the parameter set you’re trying to use you’ll get an error message.
PS> Get-VM -Name XYZ -id (New-Guid) Get-VM : Parameter set cannot be resolved using the specified named parameters. At line:1 char:1 + Get-VM -Name XYZ -id (New-Guid) + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : InvalidArgument: (:) [Get-VM], ParameterBindingException + FullyQualifiedErrorId : AmbiguousParameterSet,Microsoft.HyperV.PowerShell.Commands.GetVM
You can also use parameter sets to help control the processing within your function as this example shows:
function Convert-Temperature {
param (
[Parameter(ParameterSetName='Celsius')]
[double]$degreeC,
[Parameter(ParameterSetName='Fahrenheit')]
[double]$degreeF,
[Parameter(ParameterSetName='Kelvin')]
[double]$degreeK
)
$temps = New-Object -TypeName psobject -Property @{
'Temperature-Celsius' = 0.0
'Temperature-Fahrenheit' = 0.0
'Temperature-Kelvin' = 0.0
}
switch ($psCmdlet.ParameterSetName) {
"Celsius" {
$temps.'Temperature-Celsius' = $degreeC
$temps.'Temperature-Fahrenheit' = [math]::Round((32 + ($degreeC * 1.8)), 2)
$temps.'Temperature-Kelvin' = $degreeC + 273.15
}
"Fahrenheit" {
$temps.'Temperature-Celsius' = [math]::Round((($degreeF - 32) / 1.8), 2)
$temps.'Temperature-Fahrenheit' = $degreeF
$temps.'Temperature-Kelvin' = $temps.'Temperature-Celsius' + 273.15
}
"Kelvin" {
$temps.'Temperature-Celsius' = $degreeK - 273.15
$temps.'Temperature-Fahrenheit' = [math]::Round((32 + ($temps.'Temperature-Celsius' * 1.8)), 2)
$temps.'Temperature-Kelvin' = $degreeK
}
default {Write-Error -Message "Error!!! Should not be here" }
}
$temps
}
Each of the input parameters is in its own parameter set meaning that they are mutually exclusive – you can only use one of them!
The switch statement uses the active parameter set name to decide how to perform the relevant conversions – the output object contains the temperature in Celsius, Fahrenheit and Kelvin
under: PowerShell