C# UnionPay refund interface development (test environment) has been reported. ResponseCode = 204 & Message = Error in verifying signature. . I've been doing it for several days and want to be a master. Wrong signature format. . . When splicing strings, don't put useless characters such as spaces and double quotes in the string.

If the account number is admin, the password is admin 123456.

Signature: MD5(admin 123456)

The signatures of general interfaces are all encrypted with md5, which means the same thing. . . Look at this document carefully.