Delete Azure Resource Groups with no resources in it

Question

I am trying to find all the Azure RM resource groups with no resources in it and delete those resource groups using PowerShell. Deleting using Portal is so time consuming. Using powershell I was able to accomplish by using the following code. Is there a better way of achieving this in powershell?

$allResourceGroups = Get-AzureRmResourceGroup 

$resourceGroupsWithResources = Get-AzureRMResource | Group-Object ResourceGroupName

$allResourceGroups | % {
   $r1 = $_
   [bool]$hasResource = $false
   $resourceGroupsWithResources | % {
      if($r1.ResourceGroupName -eq $_.Name){
        $hasResource = $true
      }
   }
   if($hasResource -eq $false){
      Remove-AzureRmResourceGroup -Name $r1.ResourceGroupName -Force
   }   
}
Solution

You could try

$allResourceGroups = Get-AzureRmResourceGroup | ForEach-Object { $_.ResourceGroupName }

$resourceGroupsWithResources = Get-AzureRMResource | Group-Object ResourceGroupName | ForEach-Object { $_.Name }

$emptyResourceGroups = $allResourceGroups | Where-Object { $_ -NotIn $resourceGroupsWithResources } 

$emptyResourceGroups | ForEach-Object { Remove-AzureRmResourceGroup -Name $_ -Force }

Here they are packaged as functions that can be called

Function Get-AzureRmResourceGroupsWithNoResources {
    process {
        $allResourceGroups = Get-AzureRmResourceGroup | ForEach-Object { $_.ResourceGroupName }

        $resourceGroupsWithResources = Get-AzureRMResource | Group-Object ResourceGroupName | ForEach-Object { $_.Name }

        $emptyResourceGroups = $allResourceGroups | Where-Object { $_ -NotIn $resourceGroupsWithResources } 

        return $emptyResourceGroups
    }
}

Function Remove-AzureRmResourceGroupsWithNoResources {
    process {   
        Get-AzureRmResourceGroupsWithNoResources | ForEach-Object { Remove-AzureRmResourceGroup -Name $_ -Force }
    }
}