Question 110678 in Json Question posted in
Our archive of expertly curated questions and answers provides insights and solutions to common problems related to this popular data interchange format. From parsing and manipulating JSON data to integrating it with various programming languages and web services, our archive has got you covered. Start exploring today and take your JSON skills to the next level

Json – Error adding to array: Cannot find an overload for "Add" and the argument count: "1"

I can’t for the life of me work out how to add elements to an array inside a foreach loop.
I keep getting the error:

   8 |      $logs.Add(@{
     |      ~~~~~~~~~~~~
     | Cannot find an overload for "Add" and the argument count: "1".
MethodException: C:Usersmichael.dawsonOneDrive - Sage Software, IncDocumentsSource_Controlsecrets-dashboard-scriptfunctionCalculaterecreate-error2.ps1:8:5

I can get it to work outside of a foreach, but I’ve been scratching my head for ages 🙁
Here’s the code:

$logs = New-Object System.Collections.ArrayList
$logs = $null
$logs = @{}

Get-Service | ForEach-Object {
    $appCreds = $_

    $logs.Add(@{
        "test"      = $appCreds.DisplayName;
        "message"   = "blah"
    })
}  

$logs | ConvertTo-Json -Depth 10

Appreciate any help guys. Cheers.

I’m expecting some JSON a bit like this:

  {
    "message": "blah",
    "test": "Optimise drives"
  },
  {
    "message": "blah",
    "test": "Dell Client Management Service"
  },
  {
    "message": "blah",
    "test": "DeviceAssociationBroker_1592b90"
  }
Tags:

2

Answers


  1. 0

    Try the following:

    $logs = 
  Get-Service |
  ForEach-Object {
    @{
      test    = $_.DisplayName;
      message = "blah"
    }
  }  

$logs | ConvertTo-Json -Depth 10

    The above takes advantage of:

    • Being able to use the results of entire commands as expressions, relying on PowerShell implicitly collecting the command’s output objects in the target variable, $logs – as-is in the case of a single output object, and as an array (of type [object[]] in the case of two ore more output objects.

    • PowerShell’s implicit output behavior, where the output (result) from a command or expression is implicitly output.

    As for what you tried:

    $logs = New-Object System.Collections.ArrayList
    $logs = $null
    $logs = @{}

    Each statement overrides the previous one, so that $logs ends up containing @{}, i.e. an empty hashtable.

    Thus, a later $logs.Add(...) call with a single argument predictably fails, because a hashtable’s .Add() method requires two arguments, namely a key and and a value, separately – which isn’t what you intended, however.

    While you could have avoided this problem by making do with just $logs = New-Object System.Collections.ArrayList as the variable initialization, given that that type’s .Add() method accepts any single object to append to the list, the solution at the top shows a PowerShell-idiomatic solution that is both simpler and more efficient.

    Login or Signup to reply.
  2. 0

    I am in rush but, I want to help. Try the example below.

    $logs = New-Object System.Collections.ArrayList

Get-Service | ForEach-Object {
    $appCreds = $_

    $logs.Add(@{
        "test"      = $appCreds.DisplayName;
        "message"   = "blah"
    }) | out-null
}  

$logs | ConvertTo-Json -Depth 10
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search