Ignore (skip) column while exporting GridView to CSV using C# in ASP.Net

Hello Sir,

I'm trying to export the GridView data to CSV format, but while export the last column for edit/delete is also getting exported, please help me how to remove the last column

    public void BindGrid(GridView GridView1)
    {
        DataTable dt = new DataTable();
        // dt = obj_select.select_all();
        dt = obj_select.select_all(DropDownList4.SelectedItem.Text, DropDownList3.SelectedItem.Text);
        GridView1.DataSource = dt; // give data to GridView
        GridView1.DataBind();
        ViewState["Data"] = dt;
        con.Close();
    }
 
 
    protected void Button1_Click(object sender, EventArgs e)
    {
        if (DropDownList3.SelectedItem.Text == "------Select Year------" || DropDownList4.SelectedItem.Text == "---Select Month---")
        {
            ScriptManager.RegisterStartupScript(this, GetType(), "SweetAlert", "swal('Warning!', 'Please search the data before export!', 'warning');", true);
        }
        else
        {
            BindGrid(GridView1);
            Response.Clear();
            Response.Buffer = true;
 
            string strFileName = "Fileupload" + DateTime.Now.ToShortDateString() + ".csv";
            Response.AddHeader("content-disposition", "attachment;filename=" + strFileName);
 
            Response.Charset = "";
            Response.ContentType = "application/text";
            DataTable dt = ViewState["Data"] as DataTable;
            DataTable dt2 = new DataTable();
            for (int i = 0; i < dt.Columns.Count; i++)
            {
                dt2.Columns.Add(dt.Columns[i].ColumnName, typeof(string));
            }
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                dt2.ImportRow(dt.Rows[i]);
                dt2.Rows[i]["from"] = Convert.ToDateTime(dt2.Rows[i]["delivered_from"]).ToString("yyyy-MM-dd");
                dt2.Rows[i]["to"] = Convert.ToDateTime(dt2.Rows[i]["delivered_to"]).ToString("yyyy-MM-dd");
                 
            }
 
            this.GridView1.DataSource = dt2;
            this.GridView1.DataBind();
 
            StringBuilder sb = new StringBuilder();
            for (int k = 0; k < GridView1.Columns.Count; k++)
            {
                sb.Append(GridView1.Columns[k].HeaderText + ',');
            }
            sb.Append("\r\n");
 
            for (int i = 0; i < GridView1.Rows.Count; i++)
            {
                for (int k = 0; k < GridView1.Columns.Count; k++)
                {
                    string cell = GridView1.Rows[i].Cells[k].Text.Trim().Replace("&nbsp;", "").Replace("&quot;", "\"");
                    sb.Append("=\"" + cell + "\",");
                }
                sb.Append("\r\n");
            }
            Response.Output.Write(sb.ToString());
            Response.Flush();
            Response.End();
        }
    }

Please help

Thanks in advance