Export HTML Files into Excel using Windows Forms

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System;
using System.IO;
using Excel = Microsoft.Office.Interop.Excel;
namespace ExportData
{
    public partial class Form1: Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            string path = textBox1.Text + "/";
            var d = new DirectoryInfo(path); //Assuming Test is your Folder
            if (textBox1.Text.Length > 0)
            {
                var files = d.GetFiles("*.html"); //Getting Text files
                foreach(var file in files)
                {
                    var app = new Excel.Application();
                    try
                    {
                        var fullPathnew = d + file.Name;
                        var wb = app.Workbooks.Open(fullPathnew);
                        wb.SaveAs(d + file.Name.Replace(".html", ".xls"), Excel.XlFileFormat.xlExcel7);
                        wb.Close();
                    }
                    catch (Exception ex)
                    {
                        MessageBox.Show(ex.Message);
                    }
                    finally
                    {
                        app.Quit();
                    }
                }
            }
        }
    }
}