(C#) write excel file

cs_excel_write

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using Excel = Microsoft.Office.Interop.Excel;

namespace cs_excel_write2
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        

        private void button1_Click(object sender, EventArgs e)
        {



            //  string ExcelBookFileName = textBox3.Text;

            //  string ExcelBookFileName = "c:\\mdb\\temp2.xlsx";

            //  Microsoft.Office.Interop.Excel.Application ExcelApp
            //    = new Microsoft.Office.Interop.Excel.Application();
            Excel.Application ExcelApp
              = new Excel.Application();


            ExcelApp.Visible = true;
            Excel.Workbook wb = ExcelApp.Workbooks.Add();

            Excel.Worksheet ws1 = wb.Sheets[1];
            ws1.Select(Type.Missing);

            for (int i = 1; i < 20; i++)
            {
                Excel.Range rgn = ws1.Cells[i, 1];
                rgn.Value2 = i;
            }

            wb.SaveAs("c:\\mdb\\temp3.xlsx");
            wb.Close(false);
            ExcelApp.Quit();

        }
    }
}