Export GridView Data to Excel using OpenXml

using System;
using System.Data;
using System.IO;
using System.Web;
using System.Web.UI.WebControls;
using GridToExcel.Data;
using GridToExcel.Helper;

namespace GridToExcel
{
    public partial class Home : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                BindGrid();
            }
            SetChache();
        }

        private void SetChache()
        {
            Response.Cache.SetCacheability(HttpCacheability.Public);
            Response.Cache.SetExpires(DateTime.Now.AddYears(1));
        }

        private void BindGrid()
        {
            grdvTest.DataSource = new TestData().GetSampleData();
            grdvTest.DataBind();
        }

        protected void btnExport_Click(object sender, EventArgs e)
        {
            DataTable table = new DataTable();
            CreateTable(grdvTest, ref table);

            string file = new ExcelHelper().ExportToExcel(table);
            string rootPath = HttpContext.Current.Server.MapPath("~").ToString();
            string localCopy = Guid.NewGuid().ToString() + ".xlsx";
            File.Copy(file, rootPath + localCopy);

            Response.Redirect(localCopy);
        }

        private void CreateTable(GridView grdvTest, ref DataTable table)
        {
            // create columns
            for (int i = 0; i < grdvTest.HeaderRow.Cells.Count; i++)
                table.Columns.Add(grdvTest.HeaderRow.Cells[i].Text);

            // fill rows
            foreach (GridViewRow row in grdvTest.Rows)
            {
                DataRow dr;
                dr = table.NewRow();

                for (int i = 0; i < row.Cells.Count; i++)
                {
                    dr[i] = row.Cells[i].Text.Replace("&nbsp;", " ");
                }
                table.Rows.Add(dr);
            }
        }
    }
}