Powershell: Cannot update taxonomy type column item with multiple values

Question

I'm having a strange problem. I try to populate items' property which is of managed metadata (taxonomy) type and the update method doesn't work.

This field has "allow multiple values" property enabled and as long as I send one taxonomy type item to the field it gets stored. When I try to use more than one record and store with update on the item nothing changes.

So, it looks like this:

$item["TaxProp"] = "-1;#TaxItem1|26797705-ef0f-4d49-b7d8-f23112a325aa"
$item["TaxProp"]

After the last line I receive:

 WssId Label        TermGuid                                  ValidatedString
 ----- -----        --------                                  ---------------
 56    TaxItem1     26797705-ef0f-4d49-b7d8-f23112a325aa

Then I use $item.Update() and the data is stored properly in the list item.

But if I try to something like this:

$item2["TaxProp"] = "-1;#TaxItem1|26797705-ef0f-4d49-b7d8-f23112a325aa;#-1;#TaxItem2|c1b9fb3b-8655-4dd8-986c-cab898184d7d"
$item2["TaxProp"]

After the last line I receive:

 WssId Label        TermGuid                                  ValidatedString
 ----- -----        --------                                  ---------------
 56    TaxItem1     26797705-ef0f-4d49-b7d8-f23112a325aa
 56    TaxItem2     c1b9fb3b-8655-4dd8-986c-cab898184d7d

That is what I want to store, so I call $item2.Update()

After calling update no error occurs and nothing is stored. If I call $item2["TaxProp"] again now Powershell returns nothing.

What am I doing wrong?

Answer 1

You can set a MultiValue Managed Metadata field by creating a TaxonomyFieldValueCollection and add this collection to the field by using the SetFieldValue method.

First get the managed metadata field

A possible way ( there are more ways ) to do this is to get the field by id

$field = $item.Fields | ? {$_.Id -eq $fieldId}
$tf = [Microsoft.SharePoint.Taxonomy.TaxonomyField]$field 

Check if its a MultipleValues field and get the termset and create a TaxonomyFieldValueCollection. In the example below all available terms will be added.

if ($tf.AllowMultipleValues) {
    $ts = Get-SPTaxonomySession -Site $item.Web.Site
    $tstore = $ts.DefaultSiteCollectionTermStore
    $termSet = $tstore.GetTermSet($tf.TermSetId)
    $taxCollection = new-object Microsoft.SharePoint.Taxonomy.TaxonomyFieldValueCollection($field)
    $termSet.GetAllTerms() | %{
        $taxonomyFieldValue = new-object Microsoft.SharePoint.Taxonomy.TaxonomyFieldValue($field)
        $taxonomyFieldValue.TermGuid = $_.Id
        $taxonomyFieldValue.Label = $_.Name
        $taxCollection.Add($taxonomyFieldValue)
    }
}

If you want to add a term by Id you can use for example

$term1 = $termSet.Terms | ? {$_.Id -eq "26797705-ef0f-4d49-b7d8-f23112a325aa"} 
$taxonomyFieldValue = new-object Microsoft.SharePoint.Taxonomy.TaxonomyFieldValue($field)
$taxonomyFieldValue.TermGuid = $term1.Id
$taxonomyFieldValue.Label = $term1.Name
$taxCollection.Add($taxonomyFieldValue)

Finally add the collection to the field and update your item

$tf.SetFieldValue($item, $taxCollection)
$item.SystemUpdate($false);