As between the debtor and the assignee, notice is not necessary to enable the assignee to enforce the contract against the debtor, if the debtor has not suffered a detriment by reason of the assignee's failure to give notice.1 But until notice or knowledge the debtor is justified in treating the assignor as the party in interest, and payment by the debtor to the assignor before notice will discharge the debt in whole or in part.2 A release given by the assignor to the debtor before notice and before the debtor has knowledge of the assignment, is operative as against the assignee.3 If the debtor has actual knowledge of the assignment, the original creditor can not release him.4