>Ok, I was asked to build a dll that can be accessed from a VB program. I built a custom class that has the required code. I marked it as olepublic. I put the class in a project and then built a dll (I chose single threaded). It built a dll file. I wanted to test it from VFP so I ran a program that does a set library to that dll, additive and I get an 'Invalid dll' error.
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>Did I do something wrong? How will this work being called from VB. It should be called with parameters. I put the code in the Init of the custom class.
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You don't do SET LIBRARY at all; the OLEPUBLIC class should be registered on the PC. Ensure tha the class library that contains the OLEPUBLIC class is not included in the application, and use the ProgID of the class assigned to the in-process server to instance it:

oMyObj = CREATEOBJ('MyOLEPublic.Class', parm1, parm2, parm3)