NullArgument Exception in LINQ query

Question

The following query can throw a NullArgumentException in some cases, since items inside the m_SelectedPayabes collection can be null. How does the query need to be modified so that it doesn't throw a NullArgumentException when it encounters a null reference?

var myPayables = from payable in m_Payables
where !(from o in m_SelectedPayabes select o.PBLE.PAYABLEID).Contains(payable.PBLE.PAYABLEID)                                     
select payable;

Answer 1

You can either exclude the nulls:

var myPayables = from payable in m_Payables
                 where !(from o in m_SelectedPayabes 
                         where o != null
                         select o.PBLE.PAYABLEID).Contains(payable.PBLE.PAYABLEID)                                     
                 select payable;

Or replace the nulls with something else (assuming o.PBLE.PAYABLEID is an integer):

var myPayables = from payable in m_Payables
                 where !(from o in m_SelectedPayabes 
                         select o == null ? 0 : o.PBLE.PAYABLEID).Contains(payable.PBLE.PAYABLEID)                                     
                 select payable;