Hello,

I'm trying to create trigger on the Opportunity object to update the child Opportunity Product records with the Opportunity Owner's department number, which is one of the fields in the User object.  I'm getting the following compile error:

Error: Compile Error: Initial term of field expression must be a concrete SObject: LIST<OpportunityLineItem> at line 24 column 14

Here's the code I have.

trigger OpportunityUpdateDept on Opportunity (after update) {
    
    for( Opportunity parent: Trigger.new)
    {
    
        List<OpportunityLineItem> children = [ SELECT Department_Number__c from 
                                               OpportunityLineItem where Opportunity.id = :parent.Id];

        list <User> currentOwner = [Select User.Department_Number__c
                                            from User
                                            where User.id = :parent.ownerid];                                                       
        
        List<OpportunityLineItem> childrenToUpdate = new List<OpportunityLineItem>();
        
        for(OpportunityLineItem thischild: children )
        {
           if( thischild.Department_Number__c !=  currentOwner[0].Department_Number__c)
           {
               thischild.Department_Number__c =  currentOwner[0].Department_Number__c;
               childrenToUpdate.add(thischild);
           }
        }
        
        if( !childrenToUpdate.isEmpty)
        {
           update childrenToUpdate;
        }
    
    }                       
}

I'm not exactly sure what is causing the error.  If I remove the if statement that checks if childrentToUpdate.isEmpty, then it works.  But I want to be able to skip the update if its not necessary.  Any assistance with this issue is very much appreciated.

Thanks!