-Contains operator not working powershell

Question

All I'm trying to do is to see if the user input $month is in the array $months. But it's not liking something. Help?

Write-host "The script is to collect from the user High Tempature and Low Tempature for a day in degrees F."
$months = @("January", "February","March","April","May","June","July","August","September","October","November","December")
$finished = $false
while ($finished -eq $false){
    $month = read-host "Enter the month";
    if ($months -Contains $month)
    {
        write-host "Invalid entry"
        $finished = $false
    }
    else
    {
        $finished = $true
    }
}

JPBlanc · Accepted Answer · 2015-04-01 03:22:45Z

3

You test logic is just not the good one, just reverse youy test or reverse your actions:

Write-host "The script is to collect from the user High Tempature and Low Tempature for a day in degrees F."
$months = @("January", "February","March","April","May","June","July","August","September","October","November","December")
$finished = $false
while ($finished -eq $false){
    $month = read-host "Enter the month";
    if ($months -Contains $month)
    {
        $finished = $true
    }
    else
    {
        write-host "Invalid entry"
        $finished = $false
    }
}

answered Apr 1, 2015 at 3:22

JPBlanc

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Comments

TheMadTechnician · Accepted Answer · 2015-04-01 03:22:55Z

0

Instead of using -Contains you should just run a RegEx match using the -Match operator. Or, as you are currently testing for a negative result, use -notmatch instead. You can use your existing code, just modify it a little by joining your months with a pipe character. Like:

Write-host "The script is to collect from the user High Tempature and Low Tempature for a day in degrees F."
$months = @("January", "February","March","April","May","June","July","August","September","October","November","December")
$finished = $false
while ($finished -eq $false){
    $month = read-host "Enter the month";
    if ($month -notmatch ($months -join "|"))
    {
        write-host "Invalid entry"


     $finished = $false
    }
    else
    {
        $finished = $true
    }
}

Better yet, let's get rid of the If/Else and shorten this. Move the Join to where we define $Months, and then ask for a month and if it isn't a match ask for it again until it is with a While.

$months = @("January", "February","March","April","May","June","July","August","September","October","November","December") -join '|'
$month = read-host "Enter the month"
While($month -notmatch $months){
    "Invalid Entry"
    $month = read-host "Enter the month"
}

answered Apr 1, 2015 at 3:22

TheMadTechnician

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4 Comments

TheMadTechnician Over a year ago

@JPBlanc It works if he does it right, yes, but isn't he going to run into case sensitivity issues? Or is -contains case insensitive?

JPBlanc Over a year ago

CContains is case sensitive, not Contains.

Mike Shepard Over a year ago

I don't think switching a contains to a regex is a good trade.

TheMadTechnician Over a year ago

@MikeShepard it's been shown that comparing a RegEx match such as this has better performance than using the -contains operator, so this is a fairly common practice I think.

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