Make an Excel file hosted on SharePoint editable

Hi,

You want to edit your Read-Only file, there are no in-build function to change the File Access from Read-Only to write mode.(reference)

However, you can save this file as new workbook and edit all over there and replace it.

Steps to do it:

1) Open you excel workbook as you are having code var book = app.Workbooks.Open(fileName);

2) Save As current workbook to new workbook as like below

                  excelWorkbookObj.SaveAs(strexcelFileName);
                  excelWorkbookObj.Close();
                  excelWorkbookObj = null;

3) Open a new workbook which you saved then edit your changes and Save it.

4) Replace with the existing file.