Add key/value pair to hashtable (nested in an array, nested in a hashtable)

Question

Forgive me, but I don't know the correct terminology for this.

Assuming the following hashtable:

$ConfigurationData = @{
    AllNodes = @(
        @{
            NodeName="*"
            PSDscAllowPlainTextPassword=$True
            PsDscAllowDomainUser=$True
        }
    )
}

How do I make it look like this:

$ConfigurationData = @{
    AllNodes = @(
        @{
            NodeName="*"
            PSDscAllowPlainTextPassword=$True
            PsDscAllowDomainUser=$True
            NewItem = "SomeNewValue"
            AnotherNewItem = "Hello"
        }
    )
}

I can do:

$ConfigurationData.AllNodes += @{NewItem = "SomeNewValue"}
$ConfigurationData.AllNodes += @{AnotherNewItem  = "Hello"}

And doing $ConfgurationData.AllNodes looks right:

$ConfigurationData.AllNodes

Name                           Value                                                                                                                                            
----                           -----                                                                                                                                            
NodeName                       *                                                                                                                                                
PSDscAllowPlainTextPassword    True                                                                                                                                             
PsDscAllowDomainUser           True                                                                                                                                             
NewItem                        SomeNewValue                                                                                                                                     
AnotherNewItem                 Hello

But converting it to JSON tells a different story:

$ConfigurationData | ConvertTo-Json
{
    "AllNodes":  [
                     {
                         "NodeName":  "*",
                         "PSDscAllowPlainTextPassword":  true,
                         "PsDscAllowDomainUser":  true
                     },
                     {
                         "NewItem":  "SomeNewValue"
                     },
                     {
                         "AnotherNewItem":  "Hello"
                     }
                 ]
}

NewItem and AnotherNewItem are in their own hashtable and not in the first one and this causes DSC to throw a wobbly:

ValidateUpdate-ConfigurationData : all elements of AllNodes need to be hashtable and has a property NodeName.

I can do the following which gives me the right result:

$ConfigurationData = @{
    AllNodes = @(
        @{
            NodeName="*"
            PSDscAllowPlainTextPassword=$True
            PsDscAllowDomainUser=$True
        }
    )
}

#$ConfigurationData.AllNodes += @{NewItem = "SomeNewValue"}
#$ConfigurationData.AllNodes += @{AnotherNewItem  = "Hello"}

foreach($Node in $ConfigurationData.AllNodes.GetEnumerator() | Where-Object{$_.NodeName -eq "*"}) 
{
            $node.add("NewItem", "SomeNewValue")
            $node.add("AnotherNewItem", "Hello")
}

$ConfigurationData | ConvertTo-Json
{
    "AllNodes":  [
                     {
                         "NodeName":  "*",
                         "PSDscAllowPlainTextPassword":  true,
                         "NewItem":  "SomeNewValue",
                         "AnotherNewItem":  "Hello",
                         "PsDscAllowDomainUser":  true
                     }
                 ]
}

But this seems overkill, compared to a line like $ConfigurationData.AllNodes += @{NewItem = "SomeNewValue"}

I've also tried and failed with:

$ConfigurationData.AllNodes.GetEnumerator() += @{"NewItem" = "SomeNewValue"}

Is there a similar way to target the right "element"?

G42 · Accepted Answer · 2017-11-08 14:54:27Z

3

This line is adding an item at the array level.

$ConfigurationData.AllNodes += @{NewItem = "SomeNewValue"}

In actuality, you want to add to the first element of the array, which is your hashtable:

($ConfigurationData.AllNodes)[0] += @{"new item" = "test"}

edited Nov 8, 2017 at 14:54

answered Nov 8, 2017 at 14:42

G42

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1 Comment

woter324 Over a year ago

Thank you. So simple. Why didn't I think of that. Dsc compilation is happy too.

Mark Wragg · Accepted Answer · 2017-11-08 14:53:49Z

3

Your issue occurs because of the @() brackets you've put in your initial declaration of $ConfigurationData around the internal hashtable, which make it an array.

Per the answer from gms0ulman you need to use the array index operator to access an index of this array and then modify the properties there. E.g for the first element:

$ConfigurationData.AllNodes[0].'NewItem' = 'SomeNewValue'
$ConfigurationData.AllNodes[0].'AnotherNewItem' = 'Hello'

edited Nov 8, 2017 at 14:53

answered Nov 8, 2017 at 14:41

Mark Wragg

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2 Comments

woter324 Over a year ago

Thank you. Although the JSON output is correct, removing @(), the DSC fails to compile. Same error I cited in the Qu. (I know I didn't ask about DSC explicitly, but others may find this page hitting the same DSC problem).

Mark Wragg Over a year ago

Modified my answer, but basically gms0ulman is correct. @() is declaring allnodes as an array, which you are then populating with a hashtable, so you need to access its array index.

Manu · Accepted Answer · 2017-11-08 14:36:44Z

Actually, the only thing I didn't try:

$ConfigurationData = @{
    AllNodes = @(
        @{
            NodeName="*"
            PSDscAllowPlainTextPassword=$True
            PsDscAllowDomainUser=$True
        }
    )
}

$ConfigurationData.AllNodes.GetEnumerator().Add("NewItem","SomeNewValue")

$ConfigurationData.AllNodes.GetEnumerator().Add("AnotherNewItem","Hello")

$ConfigurationData | ConvertTo-Json




{
    "AllNodes":  [
                     {
                         "NodeName":  "*",
                         "PSDscAllowPlainTextPassword":  true,
                         "NewItem":  "SomeNewValue",
                         "AnotherNewItem":  "Hello",
                         "PsDscAllowDomainUser":  true
                     }
                 ]
}

I kind of understand the GetEnumerator bit. It creates an index - of sorts, so PS can work with the items.

But I don't get why I have to use the .Add() method and the +=@{} didn't work.

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