Update configSource of XML element in web.config using Powershell by passing in Parameters - asp.net

Question

I am trying to figure out a way to update my web.config for different environments by updating the configSource for the appSettings element in the web.config.
Here are the way I know how to do it.
$xml.get_DocumentElement().appSettings.configSource = $replaced_test
The problem is that I want one base script where I can pass in different nodes to the script that I want to change and update but I am not sure how to do it.
For example, I want to be able to call a powershell script like this
changeWebConfig.ps1 nodeToChange newValueofNode
I hope this was clear enough.
This is the code I have now.
$webConfigPath = "C:\web.config"
# Get the content of the config file and cast it to XML
$xml = [xml](get-content $webConfigPath)
#this was the trick I had been looking for
$root = $xml.get_DocumentElement()."system.serviceModel".client.configSource = $replace
# Save it
$xml.Save($webConfigPath)
The problem I was having was the configuration node
I had to change it from
<configuration xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0">
this to
<configuration>
I am not sure how to find the node with the configuration node in it's orginal state yet, but I'm getting closer.
function Set-ConfigAppSetting
([string]$PathToConfig=$(throw 'Configuration file is required'),
[string]$Key = $(throw 'No Key Specified'),
[string]$Value = $(throw 'No Value Specified'))
{
if (Test-Path $PathToConfig)
{
$x = [xml] (type $PathToConfig)
$node = $x.SelectSingleNode("//client[#configSource]")
$node.configSource = $Value
$x.Save($PathToConfig)
}
}
set-configappsetting "c:\web.config" CurrentTaxYear ".\private$\dinnernoworders" -confirm

Answer 1

Finally figured it out.
$root = $xml.get_DocumentElement().SelectSingleNode("//client[#configSource]").configSource = "test"
of course, I will replace "//client[#configSource]" with a variable so I can pass in different nodes as parameters to create my base script.

Answer 2

Im looking for a way to modify the code as well.
Here is a way you can view whats the node:
$path = 'c:\site\web.config'
$PublishState = (Select-Xml -Path $path -XPath "configuration/appSettings/add[#key='PublishState']/#value").Node.'#text'
$PublishState