pass json as parameter in power shell script - powershell

Question

I have made a function for creating new xml node.there are two parameters in my function on is a existing xml file reference and second one is element value.while running the script its showing an error
code
function createProviderNode($xmlData,$propertyValue){
Write-Host 'inside createProviderNode'
Write-Host ($propertyValue)
#[xml]$xmlData = get-content E:\powershell\data.xml
$newProviderNode = $xmlData.CreateNode("element","provider","")
$newProviderNode.SetAttribute("name",$propertyValue)
$xmlData.SelectSingleNode('providers').AppendChild($newProviderNode)
$xmlData.save("E:\powershell\data.xml")
}
did i miss anything in this code?

Answer 1

The error message implies that while you expected $xmlData to contain an object of type [xml] (System.Xml.XmlDocument) - i.e., an XML document - in reality it was a string ([string]).
In other words: When you called your createProviderNode function, the 1st argument you passed was a string, not an XML document (of type [xml]).
Typing your $xmlData parameter variable as [xml] solves this problem, as that will implicitly covert even a string argument to an XML document on demand - if possible.
A simplified example, using a script block in lieu of a function:
$xmlString = #'
<?xml version="1.0"?><catalog><book id="bk101"><title>De Profundis</title></book></catalog>
'#
# Note how $xmlData is [xml]-typed.
& { param([xml] $xmlData) $xmlData.catalog.book.title } $xmlString
The above yields De Profundis, demonstrating that the string argument was converted to an [xml] instance (which - thanks to PowerShell's type adaptation magic - makes the element names available as direct properties).
It is then safe to call the .CreateNode() method on $xmlData.

Answer 2

Well, you don't show your original XML format.
Why did you comment out that Get-Content? it will not work without it.
So, if we take the below example, it works as expected.
# Simple XML version
$SimpleXml = $null
$SimpleXml = #"
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<name>Apple</name>
<size>1234</size>
</configuration>
"#
# New node code
[xml]$XmlDoc = Get-Content -Path variable:\SimpleXml
$runtime = $XmlDoc.CreateNode("element","runtime","")
$generated = $XmlDoc.CreateNode("element","generatePublisherEvidence","")
$generated.SetAttribute("enabled","false")
$runtime.AppendChild($generated)
$XmlDoc.configuration.AppendChild($runtime)
$XmlDoc.save("$pwd\SimpleXml.xml")
Get-Content -Path "$pwd\SimpleXml.xml"
# Which creates this:
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<name>Apple</name>
<size>1234</size>
<runtime>
<generatePublisherEvidence enabled="false" />
</runtime>
</configuration>
Also Write-Host is never needed unless you are coloring screen output.
Write-Output is the default and automatically write to the screen, whether you specify Write-Output or not.
So, all of these to the same thing - output to the screen.
$SomeString = 'hello'
Write-Host $SomeString
Write-Output $SomeString
'hello'
"hello"
$SomeString
"$SomeString"
($SomeString)
("$SomeString")
$($SomeString)
# Results
hello
hello
hello
hello
hello
hello
hello
… yet, it's your choice.