How to export gridview data to CSV format in asp.net c#?

private void btnLoad_Click(object sender, EventArgs e)

        {

            using (OleDbConnection oleDbConnection = new OleDbConnection())

            {

                oleDbConnection.ConnectionString = this.textBox1.Text;

                OleDbCommand oleDbCommand = new OleDbCommand();

                oleDbCommand.CommandText = this.textBox2.Text;

                oleDbCommand.Connection = oleDbConnection;

                using (OleDbDataAdapter da = new OleDbDataAdapter(oleDbCommand))

                {

                    DataTable dt = new DataTable();

                    da.Fill(dt);

                    dataGridView1.DataSource = dt;

                }

            }

        }

    private void btnRUN_Click(object sender, EventArgs e)

        {

            TXTExport CSVExport = new TXTExport();

            CSVExport.DataSource = Spire.DataExport.Common.ExportSource.DataTable;

            CSVExport.DataTable = this.dataGridView1.DataSource as DataTable;

            CSVExport.ActionAfterExport = Spire.DataExport.Common.ActionType.OpenView;

            CSVExport.FileName = "CSV0721.csv";

            CSVExport.SaveToFile();

        }

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using System.IO;



 protected void btnExport_Click(object sender, EventArgs e)

    {

        ExportGridViewToCSV(GridView1, "myCSV");

    }

    public void ExportGridViewToCSV(GridView grdGridView, string fileName)

    {

        Response.Clear();

        Response.AddHeader("content-disposition",string.Format

			("attachment;filename={0}.csv",fileName));

        Response.Charset = "";

        Response.ContentType = "application/vnd.csv";

        StringWriter stringWrite = new StringWriter();

        HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);

        GridView1.RenderControl(htmlWrite);

        Response.Write(stringWrite.ToString());

        Response.End();

    }

    public override void VerifyRenderingInServerForm(Control control)

    {

        /* method must be implemented when using RenderControl */

    }