I use Control Panel->Region, then click on “Additional Settings”, then set List Separator to ; (semicolon) in the “Customize Format” dialog.
If I open Excel (without my office integration), fill the column 1,2,3 with “aa”, “bb”, “cc”, then save it to CSV format using either CSV (Comma delimited) (.csv) or CSV UTF-8 (Comma delimited) (.csv), then open the csv in Notepad, I could see aa;bb;cc
BUT with my office integration, doing the same thing, it always saves them as aa,bb,cc in CSV file. In my code, I have a condition that if user does not want to save it into our data base system, then the code will call
excelApp.Dialogs(Microsoft.Office.Interop.Excel.XlBuiltInDialog.xlDialogSaveAs).Show() to show the native dialog for user to save to local folder.

Thanks