What's the Maximum length for a registered COM Class?

Question

When objects get added to the Windows Registry, they show up like so:

MyNamespace.MyType

I seem to remember running into issues with my namespaces and classnames being too long when trying to register them for COM. Is there a maximum length limitation in registering classes in Windows or COM+?

Answer 1

The primary way to register COM components is by their CLSID, a fixed size 16 byte number. A GUID. You can publish a ProgID, that's useful to COM clients that need to use late binding. Like scripting languages.

I have no idea if there's a length limit to ProgIDs, there isn't one defined in the COM infrastructure. Maybe the scripting language has one. I know you are using VB6, there's no need for a ProgID at all. It prefers early binding (new ClassName, not CreateObject). Which is a good idea because late bound calls are about 10,000 times slower.

Anyhoo, if you want to specify a ProgId then use the <ProgId> attribute. The normal format is AppName.ClassName, something that should rarely test any kind of length limit.

Answer 2

Speaking of a random limit on the the "Programmatic ID"...

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Microsoft Visual Basic
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Programmatic ID string too long '<<project_name>>.<<control_name>>'.
The Programmatic ID must be 39 characters or less.
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OK   Help   
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Answer 3

• Have no more than 39 characters.
• Contain no punctuation (including underscores) except one or more periods.
• Not start with a digit.
• Be different from the class name of any OLE 1 application, including the OLE 1 version of the same application, if there is one.*

source = MSDN