Home » excel » Password Protecting an Excel file in C#

Password Protecting an Excel file in C#

Posted by: admin March 9, 2020 Leave a comment


Does anyone know the syntax for this? I’ve been looking everywhere and all I can find is C++ code for this. I’m trying to password protect an excel file programatically using the System.IO.Packaging namespace.

Any ideas?

Additional notes:

I’m NOT using the Excel interop–but instead the System.IO.Packaging namespace to encrypt and password protect the excel file.

How to&Answers:

If you want an Excel password all you need is something like this:

using Microsoft.Office.Interop.Excel

//create your spreadsheet here...

WorkbookObject.Password = password;

This requires Excel to be installed.

That’s nothing to do with System.IO.Packaging of course, so you might need to restate your question…


You will have to use the SaveAs method on the Worksheet. It has a parameter to set a password. Here is an example in VB which can be converted to C#



using System.IO;
using Excel=Microsoft.Office.Interop.Excel;

class ExcelUtil
    public  string Filename;

    private  Excel.Application oexcel;

    private Excel.Workbook obook;

    private  Excel.Worksheet osheet;
    public void createPwdExcel()
            // File name and path, here i used abc file to be 
            // stored in Bin directory in the sloution directory
            //Filename = (AppDomain.CurrentDomain.BaseDirectory + "abc.xls");
            if (File.Exists(Filename))

            if (!File.Exists(Filename))
                // create new excel application
                Excel.Application oexcel = new Excel.Application();
                oexcel.Application.DisplayAlerts = false;
                obook = oexcel.Application.Workbooks.Add(Type.Missing);
                oexcel.Visible = true;
                Console.WriteLine("Generating Auto Report");
                osheet = (Excel.Worksheet)obook.Sheets.Add(Type.Missing, Type.Missing, Type.Missing, Type.Missing);
                osheet.Name = "Test Sheet";
                osheet.get_Range("A1").Value = @"Implementing Password Security on Excel Workbook Using Studio.Net";

                osheet.get_Range("A1").Interior.ColorIndex = 5;
                osheet.get_Range("A1").Font.Bold = true;
                string password = "abc";
                obook.WritePassword = password;
                // otherwise use the folowing one
                // TODO: Labeled Arguments not supported. Argument: 2 := 'password'
                // end application object and session
                osheet = null;
                obook = null;
                oexcel = null;

        catch (Exception ex)




It’s not possible using System.IO.Packaging. You will have to use Microsoft.Office.Interop.Excel using the Worksheet.SaveAs method. This requires Excel being installed on your target system.