Example of putting -Credential in function

samplecred

$class = new-object psobject @{credential=$null}

function samplecred {
    param(
        [Parameter(Mandatory=$false)]
        [ValidateScript({("String","PSCredential") -contains $_.gettype().name})]
        [Object] $Credential      
    )
    if ($Credential) {
        switch ($Credential.gettype().name) {
            "String" {
                $class.credential = Get-Credential $credential
            }
            "PSCredential" {
                $class.credential = $credential
            }
        }        
    }
    if (!$class.credential) {
        $class.credential = Get-Credential
    }
    $class.credential
}

This is an example of my credential parameter. If the credential argument is used, it sets the credential on the underlying object being used (generally this is encapsulated in a module). Otherwise, it gets a new cred using get-credential.