PowerShell snippet for configuring <system.webServer><httpCompression>. Using this in the startup script for an Azure Cloud Service.

configure-iis-httpCompression.ps1

[xml]$config = (& "$env:WINDIR\system32\inetsrv\appcmd.exe" list config /section:httpCompression)

if ($config -ne $null -and ($config.GetElementsByTagName("httpCompression") -ne $null)) {
    $compression = $config.GetElementsByTagName("httpCompression")[0]
    
    $dynamic = $compression.dynamicTypes 
    EnableCompression $dynamic "dynamicTypes" "application/x-javascript"
    EnableCompression $dynamic "dynamicTypes" "application/atom+xml"
}

function EnableCompression([System.Xml.XmlElement]$node, [string]$nodeName, [string]$mimeType) {
    $appCmdMimeType = $mimeType.Replace("+", "%u002b")

    if (Is-CompressionSet $node $mimeType) {
        Write-Host "Compression setting for $nodeName::'$mimeType' ($appCmdMimeType) exists, clearing it..."
        & "$env:WINDIR\system32\inetsrv\appcmd.exe" set config -section:system.webServer/httpCompression /-"$nodeName.[mimeType='$appCmdMimeType']" /commit:appHost;
    }
    else {
        Write-Host "Compression for $nodeName::'$mimeType' ($appCmdMimeType) was not already set. Didn't need to clear the setting."
    }

    & "$env:WINDIR\system32\inetsrv\appcmd.exe" set config -section:system.webServer/httpCompression /+"$nodeName.[mimeType='$appCmdMimeType',enabled='True']" /commit:apphost;
}

function Is-CompressionSet([System.Xml.XmlElement]$node, [string]$mimeType) {
    return `
        ($node -ne $null) `
        -and ($node.SelectSingleNode("add[@mimeType='$mimeType']") -ne $null);
}

This is awesome, overcomes the appcmd list config inability to search for elements within the config block. Going to be using some of this in puppet module. Thank You!

Thank you! Great script!
I use it with octopus as a deployment step :-)

Lifesaver! Thanks very much for this 😀
edit: as a follow up, I found this blog which describes a PowerShell script generation feature that went in with IIS 8. Works like a charm!