How do I convert .xls file to .xlsx using c# and then edit the .xlsx file like coloring cells using epplus
<p>I wrote program to convert .xls to .xlsx, the program changes the extension but  epplus functions are not working the converted file. below is the code to convert .xls to .xlsx and color the cells of .xlsx file, the program is running without any errors or exception, but the excel is not getting edited with the colors after running the program</p>

<pre><code>using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Drawing;
using OfficeOpenXml;
using OfficeOpenXml.Style;

namespace Project42
{
class Class1
{
    static void Main(string[] args)
    {
        Console.WriteLine("File Extension Conversion From .xls to .xlsx");
        try
        {

            string filePath = @"C:\Users\mvmurthy\Desktop\abc.xls";
            if (filePath.EndsWith(".xls"))
            {
                File.Move(filePath, Path.ChangeExtension(filePath, ".xlsx"));
                Console.WriteLine("File Extension Updated To .xlsx");

            }
                FileInfo newFile = new FileInfo(@"C:\Users\mvmurthy\Downloads\abc.xlsx");
                ExcelPackage pck = new ExcelPackage(newFile);
                var ws = pck.Workbook.Worksheets["Contents"];
                ws.Cells["K:K"].Style.Fill.PatternType = ExcelFillStyle.Solid;
                ws.Cells["K:K"].Style.Fill.BackgroundColor.SetColor(Color.Yellow);
                ws.Cells["M:M"].Style.Fill.PatternType = ExcelFillStyle.Solid;
                ws.Cells["M:M"].Style.Fill.BackgroundColor.SetColor(Color.Yellow);
                ws.Cells["O:O"].Style.Fill.PatternType = ExcelFillStyle.Solid;
                ws.Cells["O:O"].Style.Fill.BackgroundColor.SetColor(Color.Yellow);
                pck.Save();


        }
        catch (Exception)
        {
            Console.WriteLine("File Extension Cannot Be Changed...Try again...");
        }
    }
}
}
</code></pre>