Excel XLL versus DLL

[Sing]

Dear Excel Gurus,

I have been writing Excel DLL. Recently, I got to know about Excel XLL
files.

Can someone advise on the pros and cons of each? Under what kind of
situation should determine our choice of using XLL or DLL?

 

[Charles Williams]

Assumimg your DLLs are VB6 DLLs then XLLs are faster because they use the C
API rather than going through the COM layer, and because complied C is
faster than compiled VB.
But only a subset of the Excel object model is exposed to the C interface
which may be a problem.
Also if you are writing application extension addins which expose an EUI
this tends to be more work in an XLL.

So the general recommendation is to use XLL when you need very fast
worksheet functions, otherwise VBA XLA or VB DLL.

Charles
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