PowerShell -- Accessing a JArray inside a JObject

Question

I have a Json object

 {
  "ProjectDirectory": "C:\\Main",
  "SiteName": "RemoteOrder",
  "ParentPath": "/Areas//Views",
  "VirtualDirectories": [
        {
          "Name": "Alerts",
          "Path": "\\Areas\\RemoteOrder\\Views\\Alerts"
        },
        {
          "Name": "Analytics",
          "Path": "\\Areas\\RemoteOrder\\Views\\Analytics"
        },
        {
          "Name": "Auth",
          "Path": "\\Areas\\RemoteOrder\\Views\\Auth"
        }
    ]
}

that I created by

$config = [Newtonsoft.Json.Linq.JObject]::Parse($file)

I can access things like

$config["ProjectDirectory"]
$config["VirtualDirectories"]

But I can not get to the element inside the VirtualDirectories JArray

I confirmed

 $config["VirtualDirectories"][0].GetType() // JObject
 $config["VirtualDirectories"].GetType() // JArray
 $config // JObject

I have tried

$config["VirtualDirectories"][0]["Name"]
$config["VirtualDirectories"][0]["Path"]
$config["VirtualDirectories"][0][0]
$config["VirtualDirectories"][0].GetValue("Name")

When I try

 $config["VirtualDirectories"][0].ToString()

I get

{
      "Name": "Alerts",
      "Path": "\\Areas\\RemoteOrder\\Views\\Alerts"
}

What I am really trying to do is access it a loop but again I can not seem to access the JObject Elements

Answer 1

You are close. $config["VirtualDirectories"][0]["Name"] will give you a JValue containing the text. You just need to use the Value property from there to get the actual string. Here is how you would do it in a ForEach loop:

$config = [Newtonsoft.Json.Linq.JObject]::Parse($file)

ForEach ($dir in $config["VirtualDirectories"])
{
    $name = $dir["Name"].Value
    $path = $dir["Path"].Value
    ...
}

Answer 2

To complement Brian Rogers' helpful answer:

As a more convenient alternative to index syntax (["<name>"]) you can use property syntax
(.<name>), because the JObject instances returned have dynamic properties named for their keys:

$config = [Newtonsoft.Json.Linq.JObject]::Parse($file)

foreach ($dir in $config.VirtualDirectories) {
  $name = $dir.Name.Value # as in Brian's answer: note the need for .Value
  $path = $dir.Path.Value # ditto
  # Sample output
  "$name=$path" # outputs 'Alerts=\Areas\RemoteOrder\Views\Alerts', ...
}

I presume that the reason you chose to work with Json.NET types directly is performance compared to PowerShell's built-in ConvertFrom-Json cmdlet.

• As an aside: There is a PowerShell wrapper for Json.NET that you can install with Install-Module -Scope CurrentUser newtonsoft.json , for instance, which implicitly gives you access to the [Newtonsoft.Json.Linq.JObject] type. However, this wrapper - which represents objects as ordered hashtables - is even slower than ConvertFrom-Json.

• Aside from performance, the following limitations of ConvertFrom-Json may make it necessary to use a third-party library such as Json.Net anyway:

  • Empty-string keys are not supported.
  • Keys that differ in case only (e.g., foo vs. Foo) are not supported.

---

For contrast, here's the equivalent - but generally slower - ConvertFrom-Json solution:

ConvertFrom-Json represents the JSON objects as [pscustomobject] instances whose properties are named for the keys, allowing for a more natural syntax without the need to access .Value:

$config = ConvertFrom-Json $json

foreach ($dir in $config.VirtualDirectories) {
  $name = $dir.Name  # no .Value needed 
  $path = $dir.Path  # ditto
  # Sample output
  "$name=$path" # outputs 'Alerts=\Areas\RemoteOrder\Views\Alerts', ...
}