Start-VMsFromWebhook.ps1

workflow Start-VMsFromWebhook
{
    param ( 
        [object]$WebhookData
    )
 
    # If runbook was called from Webhook, WebhookData will not be null.
    if ($WebhookData -ne $null) {   
 
        # Collect properties of WebhookData
        $WebhookName    =   $WebhookData.WebhookName
        $WebhookHeaders =   $WebhookData.RequestHeader
        $WebhookBody    =   $WebhookData.RequestBody
 
        # Collect individual headers. VMList converted from JSON.
        $From = $WebhookHeaders.From
        $VMList = ConvertFrom-Json -InputObject $WebhookBody
        Write-Output "Runbook started from webhook $WebhookName by $From."
 
        # Authenticate to Azure resources
        $Cred = Get-AutomationPSCredential -Name 'ContosoAccount'
        Add-AzureAccount -Credential $Cred
 
        # Start each virtual machine
        foreach ($VM in $VMList)
        {
            Write-Output "Starting $VM.Name."
            Start-AzureVM -Name $VM.Name -ServiceName $VM.ServiceName
        }
    }
    else {
        Write-Error "Runbook meant to be started only from a webhook." 
    }
}