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ERROR_SXS_DUPLICATE_WINDOWCLASS_NAME
ERROR_SXS_DUPLICATE_WINDOWCLASS_NAME means that more than one active side-by-side component contributes the same window-class name. The activation context cannot expose both registrations without ambiguity.
What to check
- Identify the two assembly manifests that define the same window-class entry.
- Consolidate the registration into one component or give independently owned classes distinct names.
- Review private assemblies introduced by plug-ins or optional modules, which can add duplicate registrations indirectly.
The fix is to remove the conflicting manifest registrations, not to change ordinary runtime window creation calls.
Microsoft: side-by-side assemblies
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