For folks who are looking for a way to do this and are fortunate enough to be using PS v3 (and my apologies for all those required to stay with V2):
The easiest way to achieve this is using the "ValidateSet" option in your input parameters.
function Show-Hello {
param (
[ValidateSet("World", "Galaxy", "Universe")]
[String]$noun
)
$greetingString = "Hello, " + $noun + "!"
Write-Host "`t=>`t" $greetingString "`t<="
}
ValidateSet throws an error if a user attempts to use any other input:
Show-Hello "Solar System"
Show-Hello : Cannot validate argument on parameter 'noun'. The argument `
"Solar System" does not belong to the set "World,Galaxy,Universe" specified `
by the ValidateSet attribute. Supply an argument that is in the set and `
then try the command again.
It also adds tab-completion to your function for that parameter. And if it is the FIRST parameter for your function, you don't even have to type in "-noun" for the tab-complete to make suggestions for its value.