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