PS: Validate-Credentials

Validate-Credentials.ps1

function Validate-Credentials([System.Management.Automation.PSCredential]$credentials)
{
    $ct = [System.DirectoryServices.AccountManagement.ContextType]::Domain
    $nc = $credentials.GetNetworkCredential()
    $principal = $nc.Domain.ToString() + "\"+ $nc.UserName.Tostring()
    $pctx = New-Object System.DirectoryServices.AccountManagement.PrincipalContext($ct, "axaros.com")

    return $pctx.ValidateCredentials($nc.UserName, $nc.Password)
}

$LogedOnUser = [System.Security.Principal.WindowsIdentity]::GetCurrent().Name;
$currentUser =  $host.ui.PromptForCredential("Need credentials", "Application Pool Identitiy", $LogedOnUser, "NetBiosUserName")

if (!(Validate-Credentials $currentUser))
{
    thorw "UPN is not correct"
}