updating/setting multiple values in lookup field through powershell

Question

I'm trying to set multiple values to lookup column. I can get it to set one value but multiple values don't work

see below

[Microsoft.SharePoint.SPFieldLookupValueCollection] $itemValues = New-Object Microsoft.SharePoint.SPFieldLookupValueCollection

[Microsoft.SharePoint.SPFieldLookupValue] $lookupvalue = New-Object Microsoft.SharePoint.SPFieldLookupValue

$lookupvalue.LookupId = 1

$lookupvalue.LookupId = 2

$itemValues.Add($lookupvalue)

$CMRSItems["Event Type"] = $itemValues
$CMRSItems.Update()

I was expecting the LookupID 1 and 2 to update but it doesn't. When i specify LookupId = 1 it works

What am i doing wrong.

Thanks in Advance

updating multivalues

$lookupvalue = GetLookUpValues -val $number
#Write-Host $lookupvalue 

[Microsoft.SharePoint.SPFieldLookupValueCollection] $itemValues = New-Object Microsoft.SharePoint.SPFieldLookupValueCollection
[Microsoft.SharePoint.SPFieldLookupValue] $lookupvalue = New-Object Microsoft.SharePoint.SPFieldLookupValue 


   #sample lookup values adding to collection: 
   #1;#Open
   #2;#Closed

$itemValues.Add($lookupvalue)

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

Getting error : Exception calling "Update" with "0" argument(s): "Invalid look-up value

Answer 1

You must create two objects of LookUpValue and add to the collection. Right now you are setting LookupID twice on the same object, overwriting the first assignment.

   [Microsoft.SharePoint.SPFieldLookupValueCollection] $itemValues = New-Object Microsoft.SharePoint.SPFieldLookupValueCollection

  [Microsoft.SharePoint.SPFieldLookupValue]    $lookupvalue = New-Object Microsoft.SharePoint.SPFieldLookupValue

  [Microsoft.SharePoint.SPFieldLookupValue]    $lookupvalue2 = New-Object Microsoft.SharePoint.SPFieldLookupValue

$lookupvalue.LookupId = 1

$lookupvalue2.LookupId = 2

 $itemValues.Add($lookupvalue)
 $itemValues.Add($lookupvalue2)

Also in your new example you seem to overwrite your $lookupvalue

$lookupvalue = GetLookUpValues -val $number
#Write-Host $lookupvalue 

[Microsoft.SharePoint.SPFieldLookupValueCollection] $itemValues = New-Object Microsoft.SharePoint.SPFieldLookupValueCollection
#[Microsoft.SharePoint.SPFieldLookupValue] $lookupvalue = New-Object Microsoft.SharePoint.SPFieldLookupValue #This row creates a new empty lookupvalue, overwriteing the one from line 1

$itemValues.Add($lookupvalue)

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

Answer 2

Add toString when updating the lookup field as shown below:

$CMRSItems["Event Type"] = $itemValues.ToString();