The opcconst.txt file declares constants for Visual Basic that are defined in the OPC specification. They are provided as part of this example. As the specification is revised these constants are subject to change and should be reviewed accordingly.
To add a text file to the project, select Add File from the Project menu.
Change the file type to All Types (*.*)
Select the opcconst.txt file, and then click Open.
The project window shows a new module named OPC Constants.
To save the new project, select Save Project from the File menu.