PowerShell script module for creating and adding guest users to Azure AD

GuestUsers.ps1

New-Module -Name GuestUsers -Scriptblock {

    $modules = Get-Module -ListAvailable AzureAD*

    if ($null -eq $modules) {
        Write-Output "Install AzureADPreview module"
        Install-Module AzureADPreview 
    }
    elseif (($modules | ?{ $_.Name -eq "AzureAD" }).Count -eq 1) {
        Write-Output "Uninstall AzureAD module and install AzureADPreview module"
        Uninstall-Module AzureAD 
        Install-Module AzureADPreview
    }

    function New-GuestUser {
        [CmdletBinding()]
        param (
            [Parameter(Mandatory=$true)]
            [ValidateNotNullOrEmpty()]
            [string] $DisplayName,

            [Parameter(Mandatory=$true)]
            [ValidateNotNullOrEmpty()]
            [string] $EmailAddress
        )

        [PSCustomObject]@{
            PSTypeName = "GuestUser"
            DisplayName = $DisplayName
            EmailAddress = $EmailAddress
        }
    }

    function Add-GuestUser {
        [CmdletBinding()]
        param (
            [Parameter(Mandatory=$true)]
            [string] $TenantId,

            [Parameter(Mandatory=$true)]
            [string] $AccountName,

            [Parameter(Mandatory=$true)]
            [string] $AccountDescription,

            [Parameter(Mandatory = $true, Position = 0, ValueFromPipeline = $true)]
            [ValidateCount(1, 65535)]
            [PSTypeName("GuestUser")]
            [PSCustomObject[]]
            $User
        )

        Begin {
            $collectedUsers = @()
        }

        Process {
            $collectedUsers += $User
        }

        End {
            Write-Output "Connect to Azure AD with Tenant ID $TenantId"
            $account = Connect-AzureAD -TenantId $TenantId
            $adUser = Get-AzureADUser -SearchString $account.Account.Id

            foreach ($collectedUser in $collectedUsers) {
                $existingUser = Get-AzureADUser -SearchString $collectedUser.EmailAddress
                if ($null -eq $existingUser -or $existingUser.UserState -eq "PendingAcceptance") {
                    $messageInfo = New-Object Microsoft.Open.MSGraph.Model.InvitedUserMessageInfo
                    $messageInfo.CustomizedMessageBody = @"
Hey $($collectedUser.DisplayName),

Please accept this invitation to join the $accountName. This account is used for $accountDescription.

Cheers,

$($adUser.DisplayName)    
"@
                    Write-Output "Send invite to $($collectedUser.EmailAddress)"
                    New-AzureADMSInvitation -InvitedUserEmailAddress $collectedUser.EmailAddress -InvitedUserDisplayName $collectedUser.DisplayName `
                                            -InviteRedirectUrl https://portal.azure.com `
                                            -InvitedUserMessageInfo $messageInfo -SendInvitationMessage $true | Out-Null
                    Write-Output "Invite sent to $($collectedUser.EmailAddress)"
                }
                else {
                    Write-Output "User $($collectedUser.DisplayName) ($($collectedUser.EmailAddress)) already exists with state $($existingUser.UserState)"
                }
            }
        }
    }

    Export-ModuleMember New-GuestUser,Add-GuestUser
}

To install

. { iwr -useb https://gist.githubusercontent.com/russcam/c763ef14fd742811a1ab5846f0e3b895/raw/31b983fb2a462b1ea710730e7f809d1261b84990/GuestUsers.ps1 } | iex;