Problem with Exporting data into Excel using C#

hello friends,

i have very big problem in C#... actually i have Export the Data Grid view into Excel.. but column name is not Exported so i don't know how can i export the Column name also... i m showing you code now you just tell me where is my Mistake.....
// code

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using Excel = Microsoft.Office.Interop.Excel;
using System.Data.OleDb;
using System.IO;
using MySql.Data.MySqlClient;
using System.Reflection;

namespace PolicySoft
{
    public partial class ExportDateWise : Form
    {
        
        private DataSet ds;

        public ExportDateWise()
        {
            InitializeComponent();
        }


        public void DataGridViewExport(String filepath)
        {
            Excel.Application xlApp;
            Excel.Workbook xlWorkBook;
            Excel.Worksheet xlWorkSheet;
            object misValue = System.Reflection.Missing.Value;
            xlApp = new Excel.ApplicationClass();
            xlWorkBook = xlApp.Workbooks.Add(misValue);
            xlWorkSheet = (Excel.Worksheet)xlWorkBook.Worksheets.get_Item(1);
            int i = 0;
            int j = 0;
            for (i = 0; i <= gv_show_dateWiseDetails.RowCount - 1; i++)
            {
                for (j = 0; j <= gv_show_dateWiseDetails.ColumnCount - 1; j++)
                {
                    DataGridViewCell cell = gv_show_dateWiseDetails[j, i];
                    xlWorkSheet.Cells[i + 1, j + 1] = cell.Value;
                }
            }
            xlWorkBook.SaveAs(filepath, Excel.XlFileFormat.xlWorkbookNormal, misValue, misValue, misValue, misValue, Excel.XlSaveAsAccessMode.xlExclusive, misValue, misValue, misValue, misValue, misValue);
            xlWorkBook.Close(true, misValue, misValue);
            xlApp.Quit();
            releaseObject(xlWorkSheet);
            releaseObject(xlWorkBook);
            releaseObject(xlApp);
            MessageBox.Show("Export SuccessFully");
        }
        private void releaseObject(object obj)
        {
            try
            {
                System.Runtime.InteropServices.Marshal.ReleaseComObject(obj);

                obj = null;
            }
            catch (Exception ex)
            {

                obj = null;

                MessageBox.Show("Exception Occured while releasing object " + ex.ToString());

            }
            finally
            {

                GC.Collect();
            }
        }

        private void btn2Excel_Click(object sender, EventArgs e)
        {

            saveFileDialog1.Filter = "Excel (*.xls)|*.xls";
            if (saveFileDialog1.ShowDialog() == DialogResult.OK)
            {
                if (!saveFileDialog1.FileName.Equals(String.Empty))
                {
                    FileInfo f = new FileInfo(saveFileDialog1.FileName);
                    if (f.Extension.Equals(".xls"))
                    {
                        DataGridViewExport(saveFileDialog1.FileName);
                    }
                    else
                    {
                        MessageBox.Show("Invalid file type");
                    }
                }
                else
                {
                    MessageBox.Show("You did pick a location to save file to");
                }
            }
        }
         
        private void btn_ok_Click(object sender, EventArgs e)
        {
            try
            {
                ds = new DataSet();
                MySqlConnection con1 = new MySqlConnection(StartUp.database);
                con1.Open();
                string str = "call ps_show_details_date_wise('" + dtp_fromDate.Value.ToString("yyyy-MM-dd") + "','" + dtp_toDate.Value.ToString("yyyy-MM-dd") + "')";
                MySqlDataAdapter da = new MySqlDataAdapter(str, con1);
                da.Fill(ds, "t_transaction");
                gv_show_dateWiseDetails.DataSource = ds.Tables[0];
                gv_show_dateWiseDetails.ReadOnly = true;
                con1.Close();
            }

            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }
}