mysql - How to export datatable to excel in c# windows application

I found some code through googling that allows me to export a data table to excel file. i successfully export the file from database table and save it in my document
My coding is:

  using System;
  using System.Data.OleDb;
  using System.Windows.Forms;
  using MySql.Data.MySqlClient;
  using System.Data;
namespace ImportFile
{
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }
    String connection = "SERVER=******;"DATABASE=dbd;"UID=root;"PASSWORD=pws;"Convert Zero Datetime = True";
 private void BExport_Click(object sender, EventArgs e)
    {
        DateTime dat = DateTime.Now;
        int time = dat.Hour;
        int time1 = dat.Minute;
        int time2 = dat.Second;
        int month = dat.Month;
        int day = dat.Day;
        MySqlConnection connection1 = new MySqlConnection(connection);
        connection1.Open();
        MySqlCommand command = new MySqlCommand ("SELECT * FROM TABLE_Name",connection1);
        MySqlDataAdapter dataadpter = new MySqlDataAdapter(command);
        DataTable datatable = new DataTable("TABLE_NAME");
        dataadpter.Fill(datatable);
        datatable.WriteXml("C:\\Users\\Downloads\\agent.xlsx" + time + " - " + time1 + " - " + time2 + " - " + day + " - " + month + "");
        MessageBox.Show("export data");
      }
     }
   }

my problem is that when i download file(click import button)its not download an excel file its just an normal file.

how i download it as excel file . if any one know this.... help me