Generate a flat list of all excel cell formulas

Question

I have a massive program written with VBA and cell formulas. I am tasked to reverse engineer it into C# winforms. I figured for a start, I need to see all the cell formulas

Answer 1

I found this answer, and tried to use the C# code by @Jake, but discovered it was slow.

Here is a faster (and complete) version:

using System;
using System.Text;
using Microsoft.Office.Interop.Excel;

namespace ExportExcelFormulas
{
    static class ExcelAccess
    {
        public static void ExportFormulasSimple(string filePath)
        {
            var app = new Application();
            var workbook = app.Workbooks.Open(filePath);
            var sCount = workbook.Sheets.Count;

            var sb = new StringBuilder();

            for (int s = 1; s <= sCount; s++)
            {
                var sheet = workbook.Sheets[s];
                var range = sheet.UsedRange;
                var f = range.Formula;

                var cCount = range.Columns.Count;
                var rCount = range.Rows.Count;

                for (int r = 1; r <= rCount; r++)
                {
                    for (int c = 1; c <= cCount; c++)
                    {
                        var id = ColumnIndexToColumnLetter(c) + "" + r + ": ";
                        var val = f[r, c];

                        if (!string.IsNullOrEmpty(val))
                        {
                            sb.AppendLine(id + val);
                            Console.WriteLine(id + val);
                        }

                    }
                }

            }

            var text = sb.ToString();
        }

        // Based on https://www.add-in-express.com/creating-addins-blog/2013/11/13/convert-excel-column-number-to-name/
        public static string ColumnIndexToColumnLetter(int i)
        {
            var l = "";
            var mod = 0;

            while (i > 0)
            {
                mod = (i - 1) % 26;
                l = (char)(65 + mod) + l;
                i = (int)((i - mod) / 26);
            }

            return l;
        }
    }
}