Problems in reading a commandline json object using powershell - json

Question

I have a powershell script "test.ps1" which takes a json string as a command line input & tries to parse it.
The powershell script is as below -
param(
[string]$json = $(throw 'test')
)
$currentPath = Get-Location
[Reflection.Assembly]::LoadFile("$currentPath\Newtonsoft.Json.dll")
$result = [Newtonsoft.Json.Linq.JObject]::Parse($json)
foreach($unit in $result["DevResults"]) {Write-Host $unit.TechnologyName.ToString()}
But it is giving me the below error -
PS C:\Users\aghosh.RJFDEV\Documents> ./test.ps1 '{"DevResults":[{"TechnologyName":"TFS","RuleName":"Alt CI ID for ESB","OutputValue":"ESClientCenter"},{"TechnologyName":"TFS","RuleName":"TFS Team Project Name","OutputValue":"ClientCenter"}],"QaResults":[{"TechnologyName":"TFS","RuleName":"Alt CI ID for ESB","OutputValue":"ESClientCenter"},{"TechnologyName":"TFS","RuleName":"TFS Team Project Name","OutputValue":"ClientCenter"}],"PreProdResults":[{"TechnologyName":"TFS","RuleName":"Alt CI ID for ESB","OutputValue":"ESClientCenter"},{"TechnologyName":"TFS","RuleName":"TFS Team Project Name","OutputValue":"ClientCenter"}],"ProdResults":[{"TechnologyName":"TFS","RuleName":"Alt CI ID for ESB","OutputValue":"ESClientCenter"},{"TechnologyName":"TFS","RuleName":"TFS Team Project Name","OutputValue":"ClientCenter"},{"TechnologyName":"TFS","RuleName":"Process Template","OutputValue":"Raymond James CMMI V3.5"}]}'
GAC Version Location
--- ------- --------
False v2.0.50727 C:\Users\aghosh.RJFDEV\documents\Newtonsoft.Json.dll
You cannot call a method on a null-valued expression.
At C:\Users\aghosh.RJFDEV\Documents\test.ps1:13 char:82
+ foreach($unit in $result["DevResults"]) {Write-Host $unit.TechnologyName.ToString <<<< ()}
+ CategoryInfo : InvalidOperation: (ToString:String) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull
You cannot call a method on a null-valued expression.
At C:\Users\aghosh.RJFDEV\Documents\test.ps1:13 char:82
+ foreach($unit in $result["DevResults"]) {Write-Host $unit.TechnologyName.ToString <<<< ()}
+ CategoryInfo : InvalidOperation: (ToString:String) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull
My powershell version is 2.0 & the Json.Net library version is 3.5.
Please help me with the error or please suggest any other suitable approach.
Thanking in advance.

Answer 1

Change this line:
foreach($unit in $result["DevResults"]) {Write-Host $unit.TechnologyName.ToString()}
To this:
foreach($unit in $result["DevResults"]) {Write-Host $unit["TechnologyName"].ToString()}