What are the situations where the transfer of creditor's rights is invalid?

According to the first paragraph of Article 545 of the Civil Code, the transfer of creditor's rights is invalid as follows: 1. Transfer is not allowed according to the nature of creditor's rights; 2, according to the agreement of the parties shall not be transferred; 3. Not transferable according to law; 4. Failure to notify the debtor. Article 546 of the Civil Code stipulates that if the creditor transfers the creditor's rights without notifying the debtor, the transfer is not effective for the debtor. The notice of assignment of creditor's rights shall not be revoked, except with the consent of the transferee. Article 547 stipulates that if a creditor assigns a creditor's right, the assignee obtains the subordinate rights related to the creditor's right, unless the subordinate rights belong exclusively to the creditor. The transferee's acquisition of subordinate rights is not affected by the failure to go through the transfer registration formalities or transfer possession of subordinate rights. Article 545 of the Civil Code of People's Republic of China (PRC), a creditor may assign all or part of his creditor's rights to a third party, except in any of the following circumstances: (1) According to the nature of his creditor's rights, he may not assign them; (two) according to the agreement of the parties shall not be transferred; (3) It shall not be transferred according to law. If the parties agree that the non-monetary creditor's rights cannot be transferred, they may not confront a bona fide third party. If the parties agree that the creditor's rights are not transferable, they may not oppose a third party.