Under any of the following circumstances, a debtor may claim set-off against the assignee: (1) When the debtor receives a notice of assignment of the claim, the debtor is owed an obligation by the assignor, and the obligation is due before or at the same time as the claim assigned. (2) The obligation owed to the debtor and the claim assigned arise from the same contract. 有下列情形之一的，债务人可以向受让人主张抵销： （一）债务人接到债权转让通知时，债务人对让与人享有债权，且债务人的债权先于转让的债权到期或者同时到期； （二）债务人的债权与转让的债权是基于同一合同产生。 Where the parties agree that a third party performs the obligation to the creditor, and the third party fails to perform the obligation, or the performance Is not in conformity with the agreement, the debtor shall be liable to the creditor for breach of contract. 当事人约定由第三人向债权人履行债务，第三人不履行债务或者履行债务不符合约定的，债务人应当向债权人承担违约责任。