How to exclude non-valued object properties when converting to JSON in Powershell

Question

I have a piece of code that works but I want to know if there is a better way to do it. I could not find anything related so far. Here are the facts:

• I have an

Answer 1

beatcracker's helpful answer offers an effective solution; let me complement it with a streamlined version that takes advantage of PSv4+ features:

# Sample input object
$object = [pscustomobject] @{
  TableName = 'MyTable'
  Description = 'Lorem ipsum dolor...'
  AppArea = 'UserMgmt'
  InitialVersionCode = $null
}

# Start with the list of candidate properties.
# For simplicity we target *all* properties of input object $obj
# but you could start with an explicit list as wellL
#   $candidateProps = 'TableName', 'Description', 'AppArea', 'InitialVersionCode'
$candidateProps = $object.psobject.properties.Name

# Create the filtered list of those properties whose value is non-$null
# The .Where() method is a PSv4+ feature.
$nonNullProps = $candidateProps.Where({ $null -ne $object.$_ })

# Extract the list of non-null properties directly from the input object
# and convert to JSON.
$object | Select-Object $nonNullProps | ConvertTo-Json

Answer 2

I have the following function in my profile for this purpose. Advantage: I can pipe a collection of objects to it and remove nulls from all the objects on the pipeline.

Function Remove-Null {
    [cmdletbinding()]
    param(
        # Object to remove null values from
        [parameter(ValueFromPipeline,Mandatory)]
        [object[]]$InputObject,
        #By default, remove empty strings (""), specify -LeaveEmptyStrings to leave them.
        [switch]$LeaveEmptyStrings
    )
    process {
        foreach ($obj in $InputObject) {
            $AllProperties = $obj.psobject.properties.Name
            $NonNulls = $AllProperties |
                where-object {$null -ne $obj.$PSItem} |
                where-object {$LeaveEmptyStrings.IsPresent -or -not [string]::IsNullOrEmpty($obj.$PSItem)}
            $obj | Select-Object -Property $NonNulls
        }
    }
}

Some examples of usage:

$AnObject = [pscustomobject]@{
    prop1="data"
    prop2="moredata"
    prop5=3
    propblnk=""
    propnll=$null
}
$AnObject | Remove-Null

prop1 prop2    prop5
----- -----    -----
data  moredata     3

$ObjList =@(
    [PSCustomObject]@{
        notnull = "data"
        more = "sure!"
        done = $null
        another = ""
    },
    [PSCustomObject]@{
        notnull = "data"
        more = $null
        done = $false
        another = $true
    }
)
$objList | Remove-Null | fl #format-list because the default table is misleading

notnull : data
more    : sure!

notnull : data
done    : False
another : True

Answer 3

Something like this?

$object = New-Object PSObject

Add-Member -InputObject $object -MemberType NoteProperty -Name TableName -Value "MyTable"
Add-Member -InputObject $object -MemberType NoteProperty -Name Description -Value "Lorem ipsum dolor.."
Add-Member -InputObject $object -MemberType NoteProperty -Name AppArea -Value "UserMgmt"
Add-Member -InputObject $object -MemberType NoteProperty -Name InitialVersionCode -Value ""

# Iterate over objects
$object | ForEach-Object {
    # Get array of names of object properties that can be cast to boolean TRUE
    # PSObject.Properties - https://msdn.microsoft.com/en-us/library/system.management.automation.psobject.properties.aspx
    $NonEmptyProperties = $_.psobject.Properties | Where-Object {$_.Value} | Select-Object -ExpandProperty Name

    # Convert object to JSON with only non-empty properties
    $_ | Select-Object -Property $NonEmptyProperties | ConvertTo-Json
}

Result:

{
    "TableName":  "MyTable",
    "Description":  "Lorem ipsum dolor..",
    "AppArea":  "UserMgmt"
}

Answer 4

I made my own modified version of batmanama's answer that accepts an additional parameter, letting you remove elements that are also present in the list present in that parameter. For example:

Get-CimInstance -ClassName Win32_UserProfile | 
Remove-Null -AlsoRemove 'Win32_FolderRedirectionHealth' | Format-Table

I've posted a gist version including PowerShell documentation as well.

Function Remove-Null {
    [CmdletBinding()]
    Param(
        # Object from which to remove the null values.
        [Parameter(ValueFromPipeline,Mandatory)]
        $InputObject,
        # Instead of also removing values that are empty strings, include them
        # in the output.
        [Switch]$LeaveEmptyStrings,
        # Additional entries to remove, which are either present in the
        # properties list as an object or as a string representation of the
        # object.
        # I.e. $item.ToString().
        [Object[]]$AlsoRemove = @()
    )
    Process {
        # Iterate InputObject in case input was passed as an array
        ForEach ($obj in $InputObject) {
            $obj | Select-Object -Property (
                $obj.PSObject.Properties.Name | Where-Object {
                    -not (
                        # If prop is null, Exclude
                        $null -eq $obj.$_ -or
                        # If -LeaveEmptyStrings is specified and the property
                        # is an empty string, Exclude
                        ($LeaveEmptyStrings.IsPresent -and
                            [string]::IsNullOrEmpty($obj.$_)) -or
                        # If AlsoRemove contains the property, Exclude
                        $AlsoRemove.Contains($obj.$_) -or
                        # If AlsoRemove contains the string representation of
                        # the property, Exclude
                        $AlsoRemove.Contains($obj.$_.ToString())
                    )
                }
            )
        }
    }
}

Note that the process block here automatically iterates a pipeline object, so the ForEach will only iterate more than once when an item is either explicitly passed in an array—such as by wrapping it in a single element array ,$array—or when provided as a direct argument, such as Remove-Null -InputObject $(Get-ChildItem).

It's also worth mentioning that both mine and batmanama's functions will remove these properties from each individual object. That is how it can properly utilize the PowerShell pipeline. Furthermore, that means that if any of the objects in the InputObject have a property that does not match (e.g. they are not null), an output table will still show that property, even though it has removed those properties from other items that did match.

Here's a simple example showing that behavior:

@([pscustomobject]@{Number=1;Bool=$true};
[pscustomobject]@{Number=2;Bool=$false},
[pscustomobject]@{Number=3;Bool=$true},
[pscustomobject]@{Number=4;Bool=$false}) | Remove-Null -AlsoRemove $false

Number Bool
------ ----
     1 True
     2
     3 True
     4