Runs in ISE, Doesn't run in powershell

ReturnedErrors.txt

At C:\Users\sancarn\AppData\Local\Temp\script.ps1:20 char:20
+         $parent = [System.Windows.Forms.TreeNode]$global:database.Ite ...
+                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Unable to find type [System.Windows.Forms.TreeNode].
At C:\Users\sancarn\AppData\Local\Temp\script.ps1:27 char:36
+ ...          [void]$node.nodes.add([System.Windows.Forms.TreeNode]::new(" ...
+                                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Unable to find type [System.Windows.Forms.TreeNode].
At C:\Users\sancarn\AppData\Local\Temp\script.ps1:33 char:45
+ ... PSCustomObject]IWDBGetChildren([System.Windows.Forms.TreeNode]$node)  ...
+                                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Unable to find type [System.Windows.Forms.TreeNode].
    + CategoryInfo          : ParserError: (:) [], ParentContainsErrorRecordException
    + FullyQualifiedErrorId : TypeNotFound

Script.ps1

        # Called with [DTP]::exec("return ""hello world""")
        class DTP {
          static [String]$IN  = "C:\Users\sancarn\AppData\Local\Temp\IN_19432.txt"
          static [String]$OUT = "C:\Users\sancarn\AppData\Local\Temp\OUT_19432.txt"
          static [String]exec([String]$script) {
            $OLD = (Get-FileHash -Path $([DTP]::OUT)).Hash
            $script |Out-File -FilePath $([DTP]::IN) -Encoding ascii
            while($OLD -eq (Get-FileHash -Path $([DTP]::OUT)).Hash){
              Start-Sleep -Milliseconds 100
            }
			
            return Get-Content -Path $([DTP]::OUT)
          }
        }

[void][System.Reflection.Assembly]::LoadWithPartialName("System.Drawing")
[void][System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms")
class API {
    static [void]addModelObject($obj){
        $parent = [System.Windows.Forms.TreeNode]$global:database.Item($obj.parent)
        $node = New-Object System.Windows.Forms.TreeNode
        $node.text = $obj.name
        $node.Tag  = $obj

        if($obj.type -eq "MODEL GROUP"){
            #add dummy child
            [void]$node.nodes.add([System.Windows.Forms.TreeNode]::new("4e84b5c3-1864-4e51-9381-6405f9d68faf"))
        }

        [void]$parent.nodes.add($node)
        [void]$global:database.add($obj.id,$node)
    }
    static [PSCustomObject]IWDBGetChildren([System.Windows.Forms.TreeNode]$node) {
        $cmd = "
            require 'json'
            iwdb = WSApplication.current_database
            mo = iwdb.model_object_from_type_and_id(""$($node.tag.type)"",$($node.tag.id))
            arr = []
            mo.children.each do |child|
                arr.push({
                    :name=>child.name,
                    :id=>child.id,
                    :type=>child.type,
                    :parent=>child.parent
                })
            end
            return arr.to_json
        "
        return ConvertFrom-Json $([DTP]::exec($cmd))
    }
	static [PSCustomObject]IWDBGetRootObjects(){
		$cmd = "
            require 'json'
            iwdb = WSApplication.current_database
            arr = []
            iwdb.root_model_objects.each do |child|
                arr.push({
                    :name=>child.name,
                    :id=>child.id,
                    :type=>child.type,
                    :parent=>child.parent
                })
            end
            return arr.to_json
        "
        return ConvertFrom-Json $([DTP]::exec($cmd))
	}
}

# DEBUG
	$rootObjects = "[{""name"":""Temp1"",""id"":1, ""type"":""MODEL GROUP"",""parent"":0},{""name"":""Temp2"",""id"":2, ""type"":""MODEL GROUP"",""parent"":0}]"
# DIST
# $rootObjects = [API]::IWDBGetRootObjects()
$rootObjects = ConvertFrom-Json $rootObjects

$form = New-Object System.Windows.Forms.Form
$form.Width = 600
$form.Height = 600

$treeView1 = New-Object System.Windows.Forms.TreeView
$System_Drawing_Size = New-Object System.Drawing.Size
$System_Drawing_Size.Width = 300
$System_Drawing_Size.Height = 300
$treeView1.Size = $System_Drawing_Size
$treeView1.Name = "treeView1"
$System_Drawing_Point = New-Object System.Drawing.Point
$System_Drawing_Point.X = 10
$System_Drawing_Point.Y = 10
$treeView1.Location = $System_Drawing_Point
$treeView1.DataBindings.DefaultDataSourceUpdateMode = 0
$treeView1.TabIndex = 0
$treeView1.Font = 'Microsoft Sans Serif,14'
$treeView1.add_BeforeExpand({
    $node = [System.Windows.Forms.TreeNode]$_.Node
    1..$node.Nodes.count | % {$node.Nodes.RemoveAt(0)}
    $children = [API]::IWDBGetChildren($node)
    ForEach($child in $children){
        [void][API]::addModelObject($child)
    }
})

$global:database = @{}
$root = New-Object System.Windows.Forms.TreeNode
$root.text = "Master Database"
$root.Name = "Master Database"
$root.Tag = "root"
[void]$treeView1.Nodes.add($root)
[void]$database.Add(0,$root)

ForEach($obj in $rootObjects){
    [void][API]::addModelObject($obj)
}

$okButton = New-Object System.Windows.Forms.Button
$okButton.width = 300
$okButton.height = 100
$okButton.top = 310
$okButton.left = 10
$okButton.add_click({
	$json = ConvertTo-Json $($treeView1.SelectedNode.Tag.id)
	Write-Host $json
})


[void]$form.Controls.Add($treeView1)
[void]$form.Controls.Add($okButton)
[void]$Form.ShowDialog()