powershell - Function parameters check -

i'm writing basic powershell libraries, , need check if specific parameter in group of values.

in example define function alv_time optional parameter. if defined, have 2 values, else signal warning. works, correct way allow parameter values or there standard way?

$warningcolor = @{"foregroundcolor" = "red"}  function avl_time {     [cmdletbinding()]     param (         $format     )      process {         # format parameter         if ($format) {             # list format possible parameters             $format_parameters = @("short: date", "long: date , time")             if ($format -like "short") {                 $now = get-date -format "yyyy-mm-dd"             }             # long date             elseif ($format -like "long") {                 $now = get-date -format "yyyy-mm-dd hh:mm:ss"             }             # if wrong format parameter             else {                 write-host @warningcolor "please use parameters:"                 $format_parameters | foreach {                     write-host @warningcolor "$_"                 }             }         }         # without format parameter         else {             $now = get-date -format "yyyy-mm-dd"         }          # return time         return $now     } } 

this check you:

param(          [validateset("short","long")]          [string]          $format ) 

example script more validations:

function foo  {      param(          [validateset("tom","dick","jane")]          [string]          $name      ,          [validaterange(21,65)]          [int]          $age      ,          [validatescript({test-path $_ -pathtype 'container'})]          [string]          $path      )      process      {          "foo $name $age $path"      }  }