updating multivalues lookup column using PowerShell in SharePoint 2013

Question

I have a multi values lookup column. I'm trying to update another column on another list from a lookup column. So let say I have values in a lookup column like so:

1;#Open 2;#Close 3;#Closed

I want to use this values to update another column that uses a lookup column. I can update if its one value e.g. 1;#Open

But when I have multiple values (e.g. the 3 of them) I get error :

Cannot convert value "Event Type" to type "System.Int32". Error: "Input string was not in a correct format."

$CMRSItems = $list.Items | where {$_['ID'] -le 5}

$CMRSItems | ForEach-Object {
$val = GetFormattedValue -val $_['Event TypeOld']
Write-Host "RefID: " $_['RefID']

$t = $val -replace ";"," "



$array = @($t)
foreach ($i in $array) {


    $c = $array.Count
    write-host $c

      $r = GetLookUpValues -val $i
      #Write-Host $r


      $documents = New-Object Microsoft.SharePoint.SPFieldLookupValueCollection($r);

      for ($i = 0; $i -lt $array.Count; $i++)
        {


           $CMRSItems["Event Type"] = $documents[$i];
           $CMRSItems.Update()

        }



 }


}



function GetFormattedValue([string]$val)
{
$tvalue = $val.Split("#") -match "\d{1,3}"
return $tvalue 
#-replace ";","`t"
}

function GetLookUpValues([string] $val)
{
foreach ($item in $lookupitem.GetItemById($val))

{
$lookupvalue = New-Object Microsoft.SharePoint.SPFieldLookupValue($item.ID,$item.Name.ToString());  

#Write-Host "lookupcol value" $lookupvalue

}
return $lookupvalue
}

Answer 1

There are various ways to get and set a lookup field

How to get a lookup field

Single value

$lookupfieldvalue = $i["lookupfield"] -as [Microsoft.SharePoint.SPFieldLookupValue]          
$lookupfieldvalue.LookupValue;

Multi value

SPFieldLookupValueCollection itemValues = item["FieldName"] as SPFieldLookupValueCollection;
foreach (SPFieldLookupValue itemValue in itemValues)
{
  int id = itemValue.LookupId;
  string value = itemValue.LookupValue;
}

How to set van value

Single value

$lookupfield = $l.Fields["lookupfield"] -as [Microsoft.SharePoint.SPFieldLookup];            
$lookuplist = $w.Lists[[Guid]$lookupfield.LookupList];            
$sourcefield =  $lookupfield.LookupField;            
$lookupitem = $lookuplist.Items[0];             

-or-

$lookupitem = $lookuplist.GetItemByUniqueId([Guid]"{fc71b84c-74d4-4f7c-9eed-fb7a5fbe24a6}")  

-or-

$lookupitem = $lookuplist.GetItemById(1)            
$lookupvalue = New-Object Microsoft.SharePoint.SPFieldLookupValue($lookupitem.ID,$lookupitem.ID.ToString());            
$i["lookupfield"] = $lookupvalue;            
$i.Update();

Multi value

SPFieldLookupValueCollection itemValues = SPFieldLookupValueCollection();
itemValues.Add(new SPFieldLookupValue(1, "Title"));
item["FieldName"] = itemValues;
item.Update();

See this document for more examples on how to set and get values with PowerShell

Answer 2

This is how it will work. Pay attention to the # sign: not in front of the first choice but all the others.

$listItem["ColumnLookupMulti"] = "1;#Open;#2;#Close;#3;#Closed"
$listItem.Update()