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Tip of the Day
Language: Visual Basic
Expertise: Beginner
Aug 8, 1997



Building the Right Environment to Support AI, Machine Learning and Deep Learning

Writing Add-ins Can Be Tricky

Writing add-ins for Visual Basic 4.0 can be challenging, rewarding, and tricky. If you are not careful writing add-ins, you can cause VB to do strange things and even abort. Although I'm sure that other diagnostics can occur, this error has appeared more than once for me while I was debugging add-ins. The messages may vary, depending on the operating system, but the result is the same.

For example, under Windows 95, you might see "This program has caused an error and will be terminated…" or "If the problem persists, contact the vendor.…" Under Windows 3.1, it may result in a GPF.

These occur when the IDE is being unloaded and will be followed on a subsequent reload of VB with this: "xxxxxx add-in could not be loaded, do you want to remove it from the list of Add-ins?"

After this, you will have to re-execute the add-in to reregister it for attachment to VB. I have found two causes for these errors:

1. Referencing a property of the VBIDE Instance Object, such as ActiveProject.Filename in the ConnectAddin Event of the Connector Class.

2. Connecting more menu or sub-menu items than you disconnect.

Most programming is an exact science, and strict adherence to "mostly undocumented" rules is an absolute necessity when writing add-ins for VB4.

Les Smith
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