How we can update droptree value of an item using PowerShell query

Question

Does anyone know how to Update droptree field values through Powershell?

We have the bulk of items, which one of the field values as __Workflow state under workflow section[while we can see enable standard template]. we need to update as a state(__Workflow state) as empty for all the items. could you please suggest how we can write a query in Powershell.

$sourcepath="master:/sitecore/content/TestFolder";
$items= Get-ChildItem -path $sourcepath -Recurse

function Update-Item{

foreach($item in $items)
{
    if($item.TemplateId -eq "{292FD0AD-CE76-4867-B43B-A58FC8F36530}")       
    {
        Write-host  "Updating Item Name and AGE:" $item.ID "";
        $rawIds = [Sitecore.Data.Fields.ReferenceField]$item.Fields["__Workflow state"]
        $item.Editing.BeginEdit()
        
        $item.Editing.EndEdit()
    }   
}

$items = Update-Item
Close-Window

Answer 1

to make a field empty you can do it using:

 $item.Editing.BeginEdit()
 $item["__Workflow state"]=""
 $item.Editing.EndEdit()

Answer 2

You can use the Reset-ItemField command to reset the workflow state to the default state. This is covered in Example 4 in the SPE book.

Reset-ItemField -Item $item -Name "__Workflow State" -IncludeStandardFields