How to add-attribute if it doesn't exist using PowerShell?

Question

In the web.config file I have to enable httpGetEnabled and httpsGetEnabled attributes if they don`t exist.

$Path = "c:\web.config"
$XPath = "/configuration/system.serviceModel/behaviors/serviceBehaviors/behavior"
if ( Select-XML -Path $Path -Xpath $XPath ) {

    "Path available"
    $attributePath = $Xpath +="/serviceMetadata" 

    "Attribute path is $attributePath"
    If (Get-XMLAttribute -Path $Path -Xpath $attributePath -attribute "httpGetEnabled" ) {

        "httpGetEnabled is present"
    }
    ElseIf (Get-XMLAttribute -Path $Path -Xpath $attributePath -attribute "httpsGetEnabled") {

        "httpsGetEnabled is present"
    }
    Else {
        "Add both httpGetEnabled and httpsGetEnabled attribute with the value true and false accordingly"
        $attributeset = @" httpGetEnabled="false" "@
        New-Attribute -path $path -xpath $XPath -attributeset $attributeset
    }

I am able to set and get attribute values using PowerShell but I don't know how to add a new attribute using PowerShell. There isno help available using Get-help for adding attributes. How to add a new attribute using PowerShell?

Solution 1

I don't know where you're getting these XML cmdlets from, but it's much easier (and recommended) to just keep the XmlDocument in memory,

$xml = [xml] (Get-Content $Path)
$node = $xml.SelectSingleNode($XPath)
...

You also don't need to use XPath for simple paths. Elements in the tree can be accessed like objects.

$httpGetEnabled = $xml.serviceMetadata.httpGetEnabled

Anyway, to add the attribute:

function Add-XMLAttribute([System.Xml.XmlNode] $Node, $Name, $Value)
{
  $attrib = $Node.OwnerDocument.CreateAttribute($Name)
  $attrib.Value = $Value
  $node.Attributes.Append($attrib)
}

To save the file back, use $xml.Save($Path)

Solution 2

On PowerShellCore 6.2 I am able to add attribute like this.

Should work on any PowerShell version.

[xml]$xml = gc my.xml
$xml.element1.element2["element3"].SetAttribute("name", "value")

This works because while using the wrapper properties on XmlElement returns wrapped values, Using the indexing operator returns a pure Xml object. The native "SetAttribute" will create one if it does not exist.

Comments

[StingyJack]

Any idea why the node must have the attribute appended and also set?

[makhdumi]

Edited for clarification. The SetAttribute was just to set the value of the attribute. It's clearer now that I used $attrib.Value = $Value before the Append.

[StingyJack]

Thanks, I wasn't sure if that was a powershell quirk or not.