Okay, thanks for your help. I think I will first go the casual route and see
whether there will be performance problems occurring at all.

But I am still wondering whether there is a COM specification for Excel.
There surely must be something like this somewhere (otherwise, how are you
supposed to build efficient AddIns?), but I cannot find it.


"Fabz" wrote in message
...
Hi there,

I am writing COMAddIns and Automation AddIns for Excel 2007 (with C#).
However, except a few sites, I cannot find any very helpful resources on
performance.

1. Does anyone know where I can find a precise description what accessing
the Excel Object Model through a COM interface really does? Am I accessing
"proxy objects" thus in fact marshalling calls from my C# code to Excel?

2. When calling myRange.Value2 do I in fact marshal a call through the COM
interface or not?

3. Question 2 leads to another question: Is is correct that using
Worksheetfunction.sum(myRange, ...) (1 marshalled call for all cells in
the range together) is much faster than using a loop and summing the cell
values in my own C# code (1 marshalled call for every single cell in the
range)?

4. When providing an Excel Range to a Worksheetfunction in my C# code,
does Excel actually remarshal the Excel Range and send it back to the
Excel application (e.g. copying all the values in the range) or does Excel
only send the cell reference (e.g. "A1:B10") to Excel and let Excel then
access the Range? Is there any way of doing something in my C# code like
Worksheetfunction.sum("A1:B10", System.Reflection.Missing.Value, ...)?

5. Does shimming my COMAddIn/Automation AddIn actually increase or
decrease performance (or doesn't it matter)?

Thanks for your answers.
Fabz