After Unregistering an add-in with COM object, Excel crashes when closing

[govert]

Due to DllCanUnload() attempting to reload the add-in during shutdown.
Reproduced in Samples\MasterSlave

[govert]

Commit 0ea3ed6 is a partial fix for this - it stops the crash but won't allow the .xll to be unloaded completely (if COM features were used).

[terryaney]

What does

won't allow the .xll to be unloaded completely (if COM features were used)

mean exactly?

[govert]

If your add-in has a ribbon or CTP, or uses the COM sever featur, or uses RTD or async functions, then the .xll file may be locked by the Excel process even after your add-in is unloaded. This means you can't delete the .xll file ntil Excel is closed.