how to use Ecel worksheet funtion in c#

hi all
i want to know how to use Excel Worksheetfunction in C#.

Welcome to the Forums.

You mean Worksheetfunction function or just worksheet functions in general?

i want to use know how to use some funtion of Ecel in C# code.

Ok, then see my C#/Excel FAQ - http://vbforums.com/showthread.php?t=406639

thanks.
i know how to do with ecel file, but my mean is: how to use some funtion in Worksheetfuntion without excel file.
ex. i want to use static funtion in excel as . average funcition

Oh, ok thats whay I asked. Then just create an Application object and access the WorksheetFunction function from it without having to create or open a workbook.