I am working on error checking in my "Copy AD User" powershell script. I use forms to ask for specific information, and the purpose of this question is to make sure i'm putting in error checking correctly.

IF ($Username.Text -eq Get-ADUser ($Username.Text)) {$wshell = New-Object -ComObject Wscript.Shell $wshell.PopUp("This username already exists. Please choose another")} 

The $Username.Text is the text box where the username for the new account is being pulled from. I want to run this through AD to see if that username already exists, and then display a message if it does.

Am I going about it the correct way?

Pastebin of Full Code

4 Answers

Here's one quick way:

([ADSISearcher] "(sAMAccountName=kendyer)").FindOne() 

If it returns no results, the user account was not found.

As a function:

function Test-ADUser { param( [Parameter(Mandatory = $true)] [String] $sAMAccountName ) $null -ne ([ADSISearcher] "(sAMAccountName=$sAMAccountName)").FindOne() } 

The problem with Get-ADUser -Identity $Username.Text is that it throws an exception when it fails to find something. If you want to avoid that, you have to search with a filter:

if (!(Get-ADUser -Filter "sAMAccountName -eq '$($Username.Text)'")) { Write-Host "User does not exist." } 

Otherwise, you can do something like:

try { Get-ADUser -Identity $Username.Text $UserExists = $true } catch [Microsoft.ActiveDirectory.Management.ADIdentityResolutionException] { Write-Host "User does not exist." $UserExists = $false } 

I use this function in many of my scripts. If you just run Test-ADUser -Username $Username, it will return the user properties AND true if the user exists and False if it does not.

If using to test a condition (does the user exist?) it will return true or false

Save the function and the export Export-ModuleMember as a .psm1 file. Example: ADutils.psm1

Create a folder with the same name as the file. Example: ADutils

Put the file in the folder

Put the folder in C:\Windows\System32\WindowsPowerShell\v1.0\Modules\

Restart power shell and import-module ADutils -verbose

(Pick a good name for the file and folder. This will be the module name. You can add a great many more functions to this module by writing the function and ensuring that the Export-ModuleMember -Function exists for every function you write)

Function Test-ADUser { [CmdletBinding()] param( [parameter(Mandatory=$true,position=0)] [string]$Username ) Try { Get-ADuser $Username -ErrorAction Stop return $true } Catch [Microsoft.ActiveDirectory.Management.ADIdentityNotFoundException] { return $false } } Export-ModuleMember -Function Test-ADUser IF (Test-ADUser -Username w096224){ (New-Object -ComObject Wscript.Shell).PopUp("This username already exists. Please choose another") } 

To answer your question directly you should probably do something like this. if Get-ADUser returns anything but $null, then the SamAccountName already exists.

IF ($null -ne $(Get-ADUser -Filter "SamAccountName -eq '$($Username.Text)'")) {$wshell = New-Object -ComObject Wscript.Shell $wshell.PopUp("This username already exists. Please choose another")} 

Explanation

You can search for each LdapDisplayName property individually. The basic syntax is:

Get-ADUser -Filter "<LdapDisplayName> -eq '<String Value>'" 

Examples

Get-ADUser -Filter "SamAccountName -eq '$SamAccountName'" Get-ADUser -Filter "UserPrincipalName -eq '$UserPrincipalName'" Get-ADUser -Filter "EmailAddress -eq '$EmailAddress'" Get-ADUser -Filter "Name -eq '$Name'" 

When Get-ADuser can't find a match it will return $null, which is easy to test for. Note that when you use the -Filter parameter Get-ADUser will NOT throw an error if an ADUser can not be found.

$ExistingADUser = Get-ADUser -Filter "SamAccountName -eq '$SamAccountName'" if($null -eq $ExistingADUser){ write-host "SamAccountName '$SamAccountName' does not yet exist in active directory" } 

how to use the filter parameter