Informix

I am creating an IfxConnection to connect to the legacy Informix server

IfxConnection con = new IfxConnection("Host=localhost;Server=myserver;UID=user;Pwd=pswd;Service=9088;Database=sysmaster")

Connection string with this set of parameters was working with some old Informix CSDK back then, but now con.Open() throws an exception "Invalid argument", and unfortunately does not say which argument exactly.

I have tried to add/remove connection string parameters in many combinations, including using parameters like Persist Security Info, Authentication, DB_LOCALE, CLIENT_LOCALE, Protocol and so on, but no luck.

Could anyone please provide a valid connection string or give me a hint what am I doing wrong?

I have found answer thanks to comment from StackOverflow
There are two versions of IBM.Data.Informix.dll - one from DB2, and another from Informix CSDK, and I was accidentally using DB2 one, because it was installed in GAC in my machine.
Version from Informix CSDK works just fine with the connection string provided.

IfxConnection con = new IfxConnection("Host=localhost;Server=myserver;UID=user;Pwd=pswd;Service=9088;Database=sysmaster")