Export GridData in Excel Sheet in Vertical Format in C# asp.net

<pre lang="cs">public void export_datagridview_to_excel(System.Windows.Forms.DataGridView dgv, string excel_file)
        {
            int cols;
            //open file
            StreamWriter wr = new StreamWriter(excel_file);

            //determine the number of columns and write columns to file
            cols = dgv.Columns.Count;
//write to excel
            for (int i = 0; i < cols; i++)
            {
                wr.Write(dgv.Columns[i].HeaderText.ToString() + "\t");
                wr.Write("\t");
                wr.Write(dgv.Rows[0].Cells[i].Value + "\r\n");
            }
            wr.Close();

        }